Software

The development and implementation of computer software is an essential part of our research activities. To this end, the linear combination of Gaussian type orbital (LCGTO) DFT program deMon2k (www.demon-software.com) was created. It implements the Hartree-Fock and Kohn-Sham methods employing the variational fitting of the Coulomb [1] and Fock [2] potentials. As a result, the calculation of four-center electron repulsion integrals (ERIs) is avoided, which eliminates the formal quartic scaling of these methods. Besides standard approaches, deMon2k also implements auxiliary density functional theory (ADFT) as developed by the Theoretical Chemistry groups at Cinvestav [3]. ADFT is a computational efficient variant of Kohn-Sham in which the real and non-interacting systems are connected by the auxiliary function density from the variational fitting of the Coulomb potential. Because this density is linear scaling, the numerical integration bottleneck of conventional DFT implementations is removed. In fact, in combination with the double asymptotic expansion of the three-center ERIs [4], the calculation of the ADFT energy and Kohn-Sham matrix elements become linear scaling and the corresponding self-consistent field calculations show excellent parallel scaling [5]. Thus, the computational bottlenecks in deMon2k ADFT calculations are shifted to linear algebra operations. To overcome these bottlenecks, we recently adapted Krylov subspace methods such as MINRES [6] and Eirola-Nevanlinna [7] for the density fitting (see Fig. 1) [8] and perturbation theory calculations [9] in deMon2k, respectively. Currently, we explore possibilities to substitute the Kohn-Sham matrix diagonalization for the solution of the Roothaan-Hall equation system by alternative lower-order scaling algorithms.

Figure 1: CPU time reduction for density fitting with the Krylov MINRES method.

A particularity of deMon2k is the implementation of perturbation theory in the framework of ADFT. The resulting auxiliary density perturbation theory (ADPT) [10] approach is a computationally efficient alternative to the common coupled-perturbed Kohn-Sham methodology. Most recently, ADPT has been used for the calculation of analytic second-order ADFT energy derivatives [11] that are needed for the calculation of molecular Hessian matrices, essential for structure optimizations, transition state searches and frequency analyses. The parallelization of these second derivative calculations show very reasonable scaling up to several hundreds of cores. This permits molecular Hessian calculations for systems with around 1,000 atoms on medium sized computational architectures.

Figure 2: Raman spectra calculation of C₆₀ Fullerene.

To calculate infrared and Raman spectra (see Fig. 2) the corresponding mixed derivatives are implemented in deMon2k, too [12]. The extension of ADPT analytic second energy derivative calculations to hybrid functionals [13] and anharmonic corrections is currently under development in the Theoretical Chemistry laboratories at Cinvestav.

To extend the application range of ADFT and ADPT to complex environments a quantum mechanical/molecular mechanical (QM/MM) hybrid approach has been implemented in deMon2k [14,15]. In QM/MM approaches a small region of a very large system is described by a QM method, whereas the computationally efficient MM force field is employed for the remaining part of the system (see Fig. 3).

Figure 3: Pictogram for the automatically generation of deMon2k input files from standard MM package topology and geometry files by QIB for QM/MM simulations.

The fundamental idea behind these QM/MM methodologies is to balance the accuracy and reliability of the simulation with the size of the underlying model. Naturally, the interface between the QM and MM regions is most delicate and defines to a large extent the achievable accuracy and reliability of the overall simulation. Therefore, it is common practice to extend the QM region as much as possible in order to diminish these interface effects. Thus, ADFT is an ideal QM method for QM/MM approaches due to its high computational efficiency that translates directly into large QM regions. Our current implementation efforts are towards NPT QM/MM simulations in deMon2k.

The current version of deMon2k is maintained and developed by a loose international consortium known as the deMon Developers with a principal node at CINVESTAV in Mexico City handling licensing (free for academics) and distribution. For further details concerning theory, implementation and program features click here (link to www.demon-software.com). The deMon2k developments of our research group are documented in the following theses in historical ordering:

• Habilitation thesis Dr. Andreas M. Köster

Entwicklung einer LCGTO-Dichtefunktionalmethode mit Hilfsfunktionen
(pdf download here)

• Ph.D. thesis Dr. José Ulises Reveles Ramírez

Geometry Optimization in LCGTO-DFT Methods

(pdf download here)

• Ph.D. thesis Dr. Roberto Flores Moreno

Analytic Derivatives in LCGTO-DFT Pseudo-Potential Methods with Auxiliary Functions
(pdf download here)

• Licenciatura thesis Q.F.B. Rodrigo Alvarez Mandez

Validation and Application of Pseudo-Potential Calculations in the Framework of the LCGTO-DFT Code deMon2k
(pdf download here)

• Ph.D. thesis Dr. Jorge Martín del Campo Ramírez

Exploring Chemical Reactivity with Auxiliary Density Functional Theory
(pdf download here)

• Ph.D. thesis Dr. Bernardo Antonio Zúñiga Gutiérrez

Magnetic Shielding, Spin-Spin Coupling Constant and Magnetizability Tensors Calculated with Auxiliary Density Perturbation Theory
(pdf download here)

• Ph.D. thesis Dr. Gabriel Ulises Gamboa Martínez

Born-Oppenheimer Molecular Dynamics with Auxiliary Density Functional Theory
(pdf download here)

• Ph.D. thesis Dr. Javier Carmona Espíndola

Time-Dependent Auxiliary Density Perturbation Theory: Method, Implementation and Applications
(pdf download here)

• Ph.D. thesis Dr. Aurelio Álvarez Ibarra

Asymptotic Expansion of Molecular Integrals in Self-Consistent Auxiliary Density Functional Methods
(pdf download here)

• Ph.D. thesis Dr. Daniel Mejía Rodríguez

Low-Order Scaling Methods for Auxiliary Density Functional Theory
(pdf download here)

• Ph.D. thesis Dr. Rogelio Isaac Delgado Venegas

Analytic Second Derivatives in Auxiliary Density Functional Theory
(pdf download here)

• Ph.D. thesis Dr. Sara Elizabeth Pérez Figueroa

Structures and Stabilities of Endohedral Fullerenes Containing Lanthanides and Actinides
(pdf download here)

• Ph.D. thesis Dr. Francisco Antonio Delesma Díaz

Range-Separated Hybrid Functionals in Auxiliary Density Functional Theory
(pdf download here)

• Ph.D. thesis Dr. Jesús Naín Pedroza Montero

Iterative Density Fitting for Ab-Initio Nanoscale Simulations
(pdf download here)

• Ph.D. thesis Dr. Adrián Amor Martínez Carranza

Symmetry Adapted Auxiliary Density Functional Theory
(pdf download here)

Reference

[1] B.I. Dunlap, J.W.D. Connolly, J.R. Sabin, J. Chem. Phys. 71, 4993 (1979).

[2] D. Mejia-Rodriguez, A.M. Köster, J. Chem. Phys. 141, 124114 (2014).

[3] P. Calaminici, A. Alvarez-Ibarra, D. Cruz-Olvera, V.D. Dominguez-Soria, R. Flores-Moreno, G.U. Gamboa, G. Geudtner, A. Goursot, D. Mejía-Rodríguez, D.R. Salahub, B. Zuniga-Gutierrez, A.M. Köster, Auxiliary Density Functional Theory: From Molecules to Nanostructures, in Handbook of Computational Chemistry, 2^nd Edition, Editors: J. Leszczynski, A. Kaczmarek-Kedziera, T. Puzyn, M. G. Papadopoulos, H. Reis, M.K. Shukla, Springer International Publishing: Chapter 18, pp. 795–860 (2017).

[4] A. Alvarez-Ibarra, A.M. Köster, J. Chem. Phys. 139, 024102 (2013).

[5] G. Geudtner, P. Calaminici, J. Carmona-Espíndola, J.M. del Campo, V.D. Dominguez-Soria, R. Flores-Moreno, G.U. Gamboa, A. Goursot, A.M. Köster, J.U. Reveles, T. Mineva, J.M. Vasquez-Perez, A. Vela, B. Zuniga-Gutierrez, D.R. Salahub, Wiley Interdisciplinary Reviews: Computational Molecular Science 2, 548 (2012).

[6] S.-C.T. Choi, C.C. Paige, M.A. Saunders, SIAM J. Sci. Comput. 33, 1810 (2011).

[7] T. Eirola, O. Nevanlinna, Linear Algebra and its Applications, 121, 511 (1989).

[8] J.N. Pedroza-Montero, J.L. Morales, G. Geudtner, A. Álvarez-Ibarra, P. Calaminici, A.M. Köster, J. Chem. Theory Comput. 16, 2965 (2020).

[9] D. Mejía-Rodríguez, R.I. Delgado-Venegas, P. Calaminici, A.M. Köster, J. Chem. Theory Comput. 11, 1493 (2015).

[10] R. Flores-Moreno, A.M. Köster, J. Chem. Phys. 128, 134105 (2008).

[11] R.I. Delgado-Venegas, D. Mejía-Rodríguez, R. Flores-Moreno, P. Calaminici, A.M. Köster, J. Chem. Phys. 145, 224103 (2016).

[12] R.I. Delgado-Venegas, P. Calaminici, A.M. Köster, Mol. Phys. 117, 1367 (2019).

[13] F.A. Delesma, G. Geudtner, D. Mejía-Rodríguez, P. Calaminici, A.M. Köster, J. Chem. Theory Comput. 14, 5608 (2018).

[14] D.R. Salahub, S.Y. Noskov, B. Lev, R. Zhang, V. Ngo, A. Goursot, P. Calaminici, A.M. Köster, A. Alvarez-Ibarra, D. Mejía-Rodríguez, J. Rezác, F. Cailliez, A. de la Lande, Molecules, 20, 4780 (2015).

[15] A. de la Lande, A. Alvarez-Ibarra, K. Hasnaoui, F. Cailliez, X. Wu, T. Mineva, J. Cuny, P. Calaminici, L. López-Sosa, G. Geudtner, I. Navizet, C. Garcia Iriepa, D.R. Salahub, A.M. Köster, Molecules 24, 1653 (2019).

Research Group

Licenciatura student

• Jorge Luis Torres Moreno

Ph.D. students

• Luis Ignacio Hernández Segura
• Juan Diego Samaniego Rojas
• Kevin Oswaldo Pérez Becerra

Postdoctoral research associates

• Dr. José De Jesús Villalobos Castro
• Dr. Jesús Naín Pedroza Montero

Publications

M.P. Lourenço, L. Barrios Herrera, J. Hostaš, P. Calaminici, A.M. Köster, A. Tchagang, D.R. Salahub, Taking the Multiplicity inside the Loop: Active Learning for Structural and Spin Multiplicity Elucidation of Atomic Clusters, Theor. Chem. Acc. 140, 116 (2021)

 J. Hostaš, A. Tchagang, M.P. Lourenço, A.M. Köster, D.R. Salahub, Global Optimization of ~1nm MoS₂ and CaCO₃ Nanoparticles, Theor. Chem. Acc. 140, 44 (2021)

 F. Louisnard, G. Geudnter, A.M. Köster, J. Cuny, Implementation of the Parallel-Tempering Molecular Dynamics Method in deMon2k and Application to the Water Hexamer, Theor. Chem. Acc. 140, 95 (2021)

 A.A.M. Carranza, A.M. Köster, Symmetry Adapted Density Fitting in Auxiliary Density Functional Theory, Theor. Chem. Acc. 140, 32 (2021)

 J.D. Samaniego-Rojas, L.-I. Hernández-Segura, L. López-Sosa, R.I. Delgado-Venegas, B. Gomez, J.-C. Lambry, A. de la Lande, T. Mineva, J. Alejandre, B.A. Zúñiga-Gutiérrez, R. Flores-Moreno, P. Calaminici, G. Geudtner, A.M. Köster, QM/MM with Auxiliary DFT in deMon2k, in Multiscale Dynamics Simulations: Nano- and Nano-bio Systems in Complex Environments, Editors: D.R. Salahub, D. Wei, RSC Theoretical and Computational Chemistry Series, London (2020)

 J.N. Pedroza-Montero, F.A. Delesma, J.L. Morales, P. Calaminici, A.M. Köster, Variational Fitting of the Fock Exchange Potential with Modified Cholesky Decomposition, J. Chem. Phys. 153, 134112 (2020)

 J.N. Pedroza-Montero, J.L. Morales, G. Geudtner, A. Álvarez-Ibarra, P. Calaminici, A.M. Köster, Variational Density Fitting with a Krylov Subspace Method, J. Chem. Theory Comput. 16, 2965 (2020)

 M. Böning, K. Dongol, G. Romero Boston, S. Schmitz, R. Wartchow, J. Samaniego-Rojas, A.M. Köster, H. Butenschön, Trifluoromethyl Substituted Benzocyclobutenone and Benzocyclobutenedione: The Structure Anomaly of (Benzocyclobutenedione)tricarbonyl-chromium Complexes, Organometallics 38, 3039 (2019)

 S. E. Pérez-Figueroa, P. Calaminici, A.M. Köster, A Hybrid ADFT Study of the C₁₀₄ and C₁₀₆ IPR Isomers, J. Phys. Chem. A 123, 4565 (2019)

A. de la Lande, A. Alvarez-Ibarra, K. Hasnaoui, F. Cailliez, X. Wu, T. Mineva, J. Cuny, P. Calaminici, L. López-Sosa, G. Geudtner, I. Navizet, C. Garcia Iriepa, D.R. Salahub, A.M. Köster, Molecular Simulations with in-deMon2k QM/MM, a Tutorial-Review, Molecules 24, 1653 (2019)

 R.I. Delgado-Venegas, P. Calaminici, A.M. Köster, Mixed Second and Third Energy Derivatives from Auxiliary Density Perturbation Theory, Mol. Phys. 117, 1367 (2019)

 F.A. Delesma, G. Geudtner, D. Mejía-Rodríguez, P. Calaminici, A.M. Köster, Range-Separated Hybrid Functionals with Variational Fitted Exact Exchange, J. Chem. Theory Comput. 14, 5608 (2018)

 J.R. Gómez-Pérez, F.A. Delesma, P. Calaminici, A.M. Köster, Accuracy of auxiliary density functional theory hybrid calculations for activation and reaction enthalpies of pericyclic reactions, J. Mol. Modeling 24, 223 (2018)

 A.M. Köster, G. Geudtner, G.U. Gamboa, A. Alvarez-Ibarra, P. Calaminici, R. Flores-Moreno, A. Goursot, A. de la Lande, D. Mejia-Rodriguez, T. Mineva, L.G.M. Pettersson, J.M. Vasquez-Perez, B. Zuniga-Gutierrez, The deMon2k User’s Guide, Version 5.0, Editors: S.B. Trickey, D.R. Salahub, http://www.deMon-software.com (2018)

 D.R. Salahub, M. Chehelamirani, S.Ahmadi, J. Hostaš, L. Barrios Herrera, D. Cruz-Olvera, P. Calaminici, A.M. Köster, Multiscale Modelling: From Clusters to Nanoparticles in Complex Environments – Insight into Mechanisms for Heavy Oil Upgrading, in Proceedings of the 18th International Conference on Computational and Mathematical Methods in Science and Engineering (2018)

 J.M. Vásquez-Pérez, A.M. Köster, P. Calaminici, The melting limit in sodium clusters, Theor. Chem. Acc. 137, 45 (2018)

 F.A. Delesma, M. Van den Bossche, H. Grönbeck, P. Calaminici, A.M. Köster, L.G.M. Pettersson, A Chemical View on X-ray Photoelectron Spectroscopy: The ESCA Molecule and Surface-to-Bulk XPS Shifts, ChemPhysChem 19, 169 (2018)

 P. Calaminici, K. Jug, A.M. Köster, Quantum Mechanics and Molecular Orbital Theory: From Basic Principles to Quantum Chemistry in Encyclopedia of Physical Organic Chemistry, Editor: Z. Wang, Wiley, DOI: 10.1002/9781118468586 (2017)

 W.H. Blades, A.C. Reber, S.N. Khanna, L. Lopez-Sosa, P. Calaminici, A.M. Köster, Evolution of the Spin Magnetic Moments and Atomic Valence of Vanadium in VCu_x⁺, VAg_x⁺, and VAu_x⁺ Clusters (x = 3 - 14), J. Phys. Chem. A 121, 2990 (2017)

A. de la Lande, C. Clavaguéra, A.M. Köster, On the Accuracy of Population Analyses Based on Fitted Densities, J. Mol. Modeling 23, 99 (2017)

R.I. Delgado-Venegas, D. Mejía-Rodríguez, R. Flores-Moreno, P. Calaminici, A.M. Köster, Analytic Second Derivatives from Auxiliary Density Perturbation Theory, J. Chem. Phys. 145, 224103 (2016)

J.N. Pedroza-Montero, F.A. Delesma, R.I. Delgado-Venegas, P. Calaminici, A.M. Köster, Static and Dynamic Polarizabilities of Oligothiophenes, Theor. Chem. Acc. 135, 230 (2016)

P. Calaminici, A. Alvarez-Ibarra, D. Cruz-Olvera, V.D. Dominguez-Soria, R. Flores-Moreno, G.U. Gamboa, G. Geudtner, A. Goursot, D. Mejía-Rodríguez, D.R. Salahub, B. Zuniga-Gutierrez, A.M. Köster, Auxiliary Density Functional Theory: From Molecules to Nanostructures, in Handbook of Computational Chemistry, Editors: J. Leszczynski, A. Kaczmarek-Kedziera, T. Puzyn, M. G. Papadopoulos, H. Reis, M.K. Shukla, Springer International Publishing: Chapter 18, pp. 795–860 (2017)

G. Geudtner, P. Calaminici, A.M. Köster, First-Principle Investigation of (Bi₂O₃)_n clusters with n=6-9, Z. Phys. Chem. 230, 991 (2016)

B. Zuniga-Gutierrez, A.M. Köster, Analytic GGA Exchange-Correlation Kernel Calculation in Auxiliary Density Functional Theory, Mol. Phys. 114, 1026 (2016)

J.M. Vásquez-Pérez, G.U. Gamboa, D. Mejía-Rodríguez, A. Alvarez-Ibarra, G. Geudtner, P. Calaminici, A.M. Köster, Influence of Spin Multiplicity on the Melting of Na₅₅⁺, J. Phys. Chem. Lett. 6, 4646 (2015)

B. Zuniga-Gutierrez, M. Camacho Gonzalez, P. Simon Bastida, A. Bendana Castillo, P. Calaminici, A.M. Köster, Efficient Calculation of Nuclear Spin-Rotation Constants from Auxiliary Density Functional Theory, J. Chem. Phys. 143, 104103 (2015)

Alvarez-Ibarra, A.M. Köster, A New Mixed Self-Consistent Field Procedure, Mol. Phys. 113, 3128 (2015)

D. Mejía-Rodríguez, X. Huang, J.M. del Campo, A.M. Köster, Hybrid Functionals with Variationally Fitted Exact Exchange, Adv. Quantum Chem. 71, 41 (2015)

A.S. Karne, N. Vaval, S. Pal, J.M. Vásquez-Pérez, A.M. Köster, P. Calaminici, Systematic comparison of DFT and CCSD dipole moments, polarizabilities and hyperpolarizabilities, Chem. Phys. Lett. 635, 168 (2015)

D. Cruz-Olvera, A. de la Trinidad Vasquez, G. Geudtner,  J.M. Vásquez-Pérez, P. Calaminici, A.M. Köster, Transition State Searches in Metal Clusters by First Principle Methods, J. Phys. Chem. A 119, 1494 (2015)

B. Zuniga-Gutierrez, M. Camacho Gonzalez, P. Simon Bastida, A. Bendana Castillo, P. Calaminici, A.M. Köster, Efficient Calculation of the Rotational g-tensor from Auxiliary Density Functional Theory, J. Phys. Chem. A 119, 1469 (2015)

D. Mejía-Rodríguez, R.I. Delgado-Venegas, P. Calaminici, A.M. Köster, Robust and Efficient Auxiliary Density Perturbation Theory Calculations, J. Chem. Theory Comput. 11, 1493 (2015)

D.R. Salahub, S.Y. Noskov, B. Lev, R. Zhang, V. Ngo, A. Goursot, P. Calaminici, A.M. Köster, A. Alvarez-Ibarra, D. Mejía-Rodríguez, J. Rezác, F. Cailliez, A. de la Lande, QM/MM Calculations with deMon2k, Molecules, 20, 4780 (2015)

A. Álvarez-Ibarra, P. Calaminici, A. Goursot, C.Z. Gómez-Castro, R. Grande-Aztatzi,    T. Mineva, D.R. Salahub, J.M. Vásquez-Pérez, A. Vela, B. Zuniga-Gutierrez, A.M. Köster, First Principles Computational Biochemistry with deMon2k, Frontiers in Computational Chemistry, Volume 2, Zaheer-Ul_Haq and J.D. Madura (Eds), Bentham Science Publishers (eBook), pp 281-325 (2015)

G. Geudtner, V.D. Domínguez-Soria, P. Calaminici, A.M. Köster, Molecular Graphs of Li_n, Na_n and Cu_n (n=6-9) Clusters from the Density and the Molecular Electrostatic Potential, Comp. Theor. Chem. 1053, 337 (2015)

D. Mejia-Rodriguez, A.M. Köster, Robust and Efficient Variational Fitting of Fock Exchange, J. Chem. Phys. 141, 124114 (2014)

V.M. Medel, A.C. Reber, V. Chauhan, P. Sen, A.M. Köster, P. Calaminici, S.N. Khanna, Nature of Valence Transition and Spin Moment in Ag_nV⁺ Clusters, J. Am. Chem. Soc. 136, 8229 (2014)

J.M. Vásquez-Pérez, P. Calaminici, A.M. Köster, Heat Capacities from Born-Oppenheimer Molecular Dynamics Simulations: Al₂₇⁺ and Al₂₈⁺, Comp. Theor. Chem. 1021, 229 (2013)

P. Calaminici, M. Perez-Romero, J.M. Vasquez-Perez, A.M. Köster, On the Ground State Structure of Neutral Cu_n (n=12, 14, 16, 18, 20) Clusters, Comp. Theor. Chem. 1021,41 (2013)

A.M. Köster, A. Goursot, D.R. Salahub, deMon2k in Reference Module in Chemistry, Molecular Science and Chemical Engineering, Editor: J. Reedijk, Elsevier, Amsterdam (2013).

J. Carmona-Espíndola, A.M. Köster, Photoabsorption Spectra from Time-Dependent Auxiliary Density Functional Theory, Can. J. Chem. 91, 795 (2013)

G. Geudtner, P. Calaminici, A.M. Köster, Growth Pattern of (Bi₂O₃)_n with n=1-5: A First Principle Investigation, J. Phys. Chem. C 117, 13210 (2013)

A. Alvarez-Ibarra, A.M. Köster, Double Asymptotic Expansion of Three-Center Electronic Repulsion Integrals, J. Chem. Phys. 139, 024102 (2013)

X. Liu, A. Tkalych, B. Zhou, A.M. Köster, D.R. Salahub, Adsorption of Hexacyclic C₆H₆, C₆H₈, C₆H₁₀ and C₆H₁₂ on a Mo-Terminated a-Mo₂C (0001) Surface, J. Phys. Chem. C 117, 7069 (2013)

A. de la Lande, D.R. Salahub, A.M. Köster, Extending the Domain of Application of Constrained Density Functional Theory to Large Molecular Systems in Concepts and Methods in Modern Theoretical Chemistry, Vol. 1: Electronic Structure and Reactivity, Editors: Ghosh and Chatteraj, CRC Press, Boca Raton (2013)

A. Goursot, T. Mineva, J.M. Vasquez, P. Calaminici, A.M. Köster, D.R. Salahub, Contribution of High-Energy Conformations to NMR Chemical Shifts, a DFT-BOMD Study, Phys. Chem. Chem. Phys. 15, 860 (2013)

S.V. Shedge, S. Pal, A.M. Köster, Theoretical Study of Frequency and Temperature Dependence of Dipole-Quadrupole Polarizability of P₄ and Adamantane, Chem. Phys. Lett. 552, 146 (2012)

A. Alvarez-Ibarra, A.M. Köster, R. Zhang, D.R. Salahub, Asymptotic expansion for electrostatic embedding integrals in QM/MM calculations, J. Chem. Theory Comput. 8, 4232 (2012)

V.D. Dominguez-Soria, P. Calaminici, A.M. Köster, Variational Fitting in Auxiliary Density Functional Theory, in Theoretical and Computational Developments in Modern Density Functional Theory, Editor: A.K. Roy, Nova Science Publisher, NY, USA (2012)

G.U. Gamboa, P. Calaminici, A.M. Köster, Development of Barostats for Finite Systems Born-Oppenheimer Molecular Dynamics Simulations, J. Mex. Chem. Soc. 56, 279 (2012)

B. Zuniga-Gutierrez, G. Geudtner, A.M. Köster, Magnetizability Tensors from Auxiliary Density Functional Theory, J. Chem. Phys. 137, 094113 (2012)

P. Calaminici, V.D. Dominguez-Soria, A.M. Köster, Comparison of Molecular Graphs of Li_n, Na_n and Cu_n (n=2-5) Clusters Obtained from the Density and the Molecular Electrostatic Potential, Int. J. Quantum Chem. 112, 3624 (2012)

J. Carmona-Espíndola, R. Flores-Moreno, A.M. Köster, Static and Dynamic First Hyperpolarizabilities from Time-Dependent Auxiliary Density Perturbation Theory, Int. J. Quantum Chem. 112, 3461 (2012)

P. Calaminici, J. Carmona-Espíndola, G. Geudtner, A.M. Köster, Static and Dynamic  Polarizability of C₅₄₀ Fullerene, Int. J. Quantum Chem. 112, 3252 (2012)

J.U. Reveles, A.M. Köster, P. Calaminici, S.N. Khanna, Structural Changes in Pd₁₃ upon Charging and Oxidation/Reduction, J. Chem. Phys. 136, 114505 (2012)

G. Geudtner, P. Calaminici, J. Carmona-Espíndola, J.M. del Campo, V.D. Dominguez-Soria, R. Flores-Moreno, G.U. Gamboa, A. Goursot, A.M. Köster, J.U. Reveles, T. Mineva, J.M. Vasquez-Perez, A. Vela, B. Zuniga-Gutierrez, D.R. Salahub, deMon2k, Wiley Interdisciplinary Reviews: Computational Molecular Science 2, 548 (2012)

P. Calaminici, V.D. Dominguez-Soria, R. Flores-Moreno, G.U. Gamboa, G. Geudtner, A. Goursot, D.R. Salahub, A.M. Köster, Auxiliary Density Functional Theory: From Molecules to Nanostructures, in Handbook of Computational Chemistry, Editor: J. Leszczynski Springer-Verlag, Berlin, Heidelberg (2011)

A.M. Köster, G. Geudtner, P. Calaminici, M.E. Casida, R. Flores-Moreno, G.U. Gamboa, A. Goursot, F. Janetzko, J.U. Reveles, A. Vela, B. Zuniga-Gutierrez, The deMon2k User’s Guide, Version 3.0, Editors: S.B. Trickey, D.R. Salahub, http://www.deMon-software.com (2011)

A.M. Köster, First-Principle Property Calculations for Large Molecules with Auxiliary Density Perturbation Theory, in Proceedings of the 10th International Conference on Computational and Mathematical Methods in Science and Engineering (2011)

A.M. Köster, P. Calaminici, E. Orgaz, D.R. Roy, J.U. Reveles, S.N. Khanna, On the Ground State of Pd₁₃, J. Am. Chem. Soc. 133, 12192 (2011)

S.V. Shedge, S. Pal, A.M. Köster, Validation and Application of Auxiliary Density Perturbation Theory and Non-Iterative Approximation to Coupled-Perturbed Kohn-Sham Approach for Dipole-Quadrupole Polarizability Calculation, Chem. Phys. Lett. 510, 185 (2011)

D.R. Salahub, P. Calaminici, G.U. Gamboa, A.M. Köster, J.M. Vasquez, Density Functional Calculation of Metal Clusters: Structure, Dynamics and Reactivity, in Metallic Systems: A Quantum Chemist's Perspective, Editors: T.C. Allison, O. Coskuner, C.A. Gonzalez, CRC Press, Boca Raton (2011)

B. Zuniga-Gutierrez, G. Geudtner, A.M. Köster, NMR Shielding Tensors from Auxiliary Density Functional Theory, J. Chem. Phys. 134, 124108 (2011)

R. Flores-Moreno, J. Carmona-Espíndola, A.M.  Köster, Calculation of Hyper-polarizabilities with Auxiliary Density Perturbation Theory, Lecture Volume of the International Conference on Computational Methods in Science and Engineering, American Institute of Physics (2011)

P. Calaminici, A.M. Köster, J.M. Vasquez-Perez, G.U. Gamboa, Metal Cluster Structures and Properties from Born-Oppenheimer Molecular Dynamics, Lecture Volume of the International Conference on Computational Methods in Science and Engineering, American Institute of Physics (2011)

P. Calaminici, A.M. Köster, Z. Gómez-Sandoval, Are Dicationic Chalcogenid Ring Systems Aromatic? in Aromaticity and Metal Clusters, Editor: P.K. Chattaraj, CRC Press, Boca Raton (2010)

J. Carmona-Espíndola, R. Flores-Moreno, A.M.  Köster, Time-Dependent Auxiliary Density Perturbation Theory, J. Chem. Phys. 133, 084102 (2010)

J.U. Reveles, A.M. Köster, S. Khanna, C. Quintanar, Surface Oxygen Diffusion into Neutral, Cationic, and Dicationic Vacancies on MgO(100) Surfaces, J. Phys. Chem. C 114, 12265 (2010)

S.V. Shedge, J. Carmona-Espíndola, S. Pal, A.M. Köster, Comparison of Auxiliary Density Perturbation Theory and Non-Iterative Approximation to Coupled Perturbed Kohn-Sham Method: Case Study of Polarizabilities of Disubstituted Azoarene Molecules, J. Phys. Chem. A 114, 2357 (2010)

G.U. Gamboa, J.M. Vasquez-Perez, P. Calaminici, A.M. Köster, Influence of Thermostats on the Calculation of Heat Capacities from Born-Oppenheimer Molecular Dynamics Simulations, Int. J. Quantum Chem. 110, SI2172 (2010)

M. Dessens-Felix, R. Pacheco-Contreras, C. Cruz-Vazquez, A. Posada-Amarillas, A.M. Köster, A Theoretical Kohn-Sham DFT based study on Pt@Pd₁₂, J. Comput. Theor. Nanosci. 7, 1 (2010)

F. Janetzko, A. Goursot, T. Mineva, P. Calaminici, R. Flores-Moreno, A.M. Köster, D.R. Salahub, Structure Determination of Clusters: Bridging Experiment and Theory, in Nanoclusters: A Bridge across Disciplines, Editors: P. Jena, A. Castleman, Jr., Elsevier (2010)

J.M. Vasquez-Perez, G.U. Gamboa, A.M. Köster, P. Calaminici, The Discovery of unexpected Isomers in Sodium Heptamers by Born-Oppenheimer Molecular Dynamics, J. Chem. Phys. 131, 124126 (2009)

V.D. Dominguez-Soria, G. Geudtner, J.L. Morales, P. Calaminici, A.M. Köster, Robust and Efficent Density Fitting, J. Chem. Phys. 131, 124102 (2009)

A.M. Köster, J.M. del Campo, F. Janetzko, B. Zuniga-Gutierrez, A Minmax Self-Consistent-Field Approach for Auxiliary Density Functional Theory, J. Chem. Phys. 130, 114106 (2009)

J.M. del Campo, A.M. Köster, The Importance of Step Control in Optimization Methods, Croatica Chemica Acta 82, 283 (2009)

P. Calaminici, G. Geudtner, A.M. Köster, First-Principle Calculations of Large Fullerenes, J. Chem. Theory Comput.  5, 29 (2009)

J.I. Rodríguez, A.M. Köster, P.W. Ayers, A. Santos-Valle, A. Vela, G. Merino, An efficient grid-based scheme to compute QTAIM atomic properties without explicit calculation of zero-flux surfaces, J. Comp. Chem. 30, 1082 (2009)

G.U. Gamboa, P. Calaminici, G. Geudtner, A.M. Köster, How Important are Temperature Effects for Cluster Polarizabilities?, J. Phys. Chem. A 112, 11969 (2008)

R. Caballero, C. Quintanar, A.M. Köster, S.N. Khanna, J.U. Reveles, Structural and Electronic Properties of Au and Au₂ on an MgO(100) Surface: A DFT Cluster Embedding Approach, J. Phys. Chem. C 112, 14919 (2008)

J.M. del Campo, A.M. Köster, A Hierarchical Transition State Search Algorithm, J. Chem. Phys. 129, 024107 (2008)

J.I. Rodríguez, D.C. Thompson, P.W. Ayers, A.M. Köster, Numerical integration of exchange-correlation energies and potentials using transformed sparse grids, J. Chem. Phys. 128, 224103 (2008)

F. Janetzko, T. Bredow, G. Geudtner, A.M. Köster, Boron doped diamond: Investigation of the stability of surface doping versus bulk doping using cyclic cluster model calculations, J. Comp. Chem. 29, 2295 (2008)

R. Flores-Moreno, A.M. Köster, Auxiliary Density Perturbation Theory, J. Chem. Phys. 128, 134105 (2008)

F. Janetzko, A.M. Köster, D.R. Salahub, Development of the cyclic cluster model formalism for Kohn-Sham auxiliary density functional theory methods, J. Chem. Phys. 128, 024102 (2008)

P. Calaminici, V.D. Dominguez-Soria, G. Geudtner, A.M. Köster, Molecular Graphs of Li_n Clusters (n=2-6) from the Density and the Molecular Electrostatic Potential, J. Comp. Methods in Sciences and Engineering 7, 383 (2007)

J.U. Reveles, P. Calaminici, M.R. Beltran, A.M. Köster, S.N. Khanna, H₂O Nucleation around Au⁺, J. Am. Chem. Soc. 129, 15565 (2007)

N.M. Reilly, J.U. Reveles, G.E. Johnson, J.M. del Campo, S.N. Khanna, A.M. Köster, A.W. Castleman Jr., Experimental and Theoretical Study of the Structure and Reactivity of Fe_mO_n⁺ (m=1-2, n=1-5) with CO, J. Phys. Chem. C, 111, 19086 (2007)

P. Calaminici, A.M. Köster, Z. Gómez, A Density Functional Study of the Structure and Properties of Cu₉ and Cu₉^-, J. Chem. Theory Comput. 3, 905 (2007)

Z. Gómez, P. Calaminici, A.M. Köster, B. Lotina-Hennsen, B. King-Díaz, N. Macías Ruvalcaba, M. Aguilar-Martínez, M. Jiménez-Estrada, Density Functional Study of 2-[(R-Phenyl) Amine]-1,4-Naphthalendiones, J. Chem. Theory Comput. 3, 894 (2007)

P. Calaminici, F. Janetzko, A.M. Köster, R. Mejia-Olvera, B. Zuniga-Gutierrez, DFT Optimized Basis Sets for Gradient Corrected Functionals: 3d Transition Metal Systems, J. Chem. Phys. 126, 044108 (2007)

N. Jardillier, D. Berthomieu, A. Goursot, J.U. Reveles, A.M. Köster, Theoretical Study of Cu^I-Y Zeolite: Structure and Electronic Properties, J. Phys. hem. B 110, 18440 (2006)

A. Ipatov, A. Fouqueau, C. Perez del Valle, F. Cordova, M.E. Casida, A.M. Köster, A. Vela, Excitation Energies from an Auxiliary Function Formulation of Time-Dependent Density-Functional Response Theory with Charge Conservation Constraint, J. Mol. Structure: THEOCHEM 762, 179 (2006)

J.U. Reveles, S.N. Khanna, A.M. Köster, Equivalent Delocalized Internal Coordinates, J. Mol. Structure: THEOCHEM 762, 171 (2006)

P. Calaminici, A.M. Köster, K. Jug, D. Gray, W. Blau, Geometrical Effect on the First Hyperpolarizability of Thiophene-Substituted Stilbene Derivatives, J. Mol. Structure: THEOCHEM 762, 87 (2006)

B. King-Díaz, N.A. Macías-Ruvalcaba, M. Aguilar-Martínez, P. Calaminici, A.M. Köster, Z. Gómez-Sandoval, J.U. Reveles, B. Lotina-Hennsen, 2-[(R-Phenyl)amine-1,4-naphthalendiones as photosystem I electron acceptors.  Structure-activity relationship of m- and p-PAN compounds with QSAR analysis, Journal of Photochemistry and Photobiology B: Biology 83, 105 (2006)

R. Flores-Moreno, R.J. Alvarez-Mendez, A. Vela, A.M. Köster, Half-Numerical Evaluation of Pseudo-Potential Integrals, J. Comp. Chem. 27, 1009, (2006)

G. Geudtner, F. Janetzko, A.M. Köster, A. Vela, P. Calaminici, Parallelization of the deMon2k code, J. Comp. Chem. 27, 483 (2006)

P. Calaminici, V.D. Domínguez-Soria, G. Geudtner, E. Hernández-Marín, A.M. Köster, Parallelization of Three-Center-Electron Repulsion Integrals, Theor. Chem. Acc. 115, 221 (2006)

P. Calaminici, R. Flores-Moreno, A.M. Köster, A Density Functional Study of Structures and Vibrations of Ta₃O and Ta₃O^-, Computing Letters 1, 164 (2005)

D.R. Salahub, J. Weber, A. Goursot, A.M. Köster, A. Vela, Applied Density Functional Theory and the deMon Code, 1964 - 2004, in Theory and Applications of the Computational Chemistry: The First 40 Years, Editors: C.E. Dykstra, G. Frenking, K.S. Kim, G. Scuseria, Elsevier (2005)­­

R.F. Nalewajski, A.M. Köster, S. Escalante, Electron Localization as Information Measure, J. Phys. Chem. A 109, 10038 (2005)

A.M. Köster, T. Bredow, Editorial: The 65th birthday of Karl Jug, Theor. Chem. Acc. 114, 1 (2005)

J.U. Reveles, T. Heine, A.M. Köster, ¹³C NMR pattern of Sc₃N@C₆₈ − Structural Assignment of the First Fullerene with Adjacent Pentagons, J. Phys. Chem. A 109, 7068 (2005)

P. Calaminici, V.D. Domínguez-Soria, G. Geudtner, E. Hernández-Marín, A.M. Köster, Parallelization of the Variational Fitting of the Coulomb Potential, Revista Superficies y Vacío 18, 1 (2005)

A.M. Köster, G. Geudtner, Z. Gómez, P. Calaminici, First Principle s and p Energy Separation, J. Phys. Chem. A 109, 1257 (2005)

A.M. Köster, P. Calaminici, S. Escalante, R. Flores-Moreno, A. Goursot, S. Patchkovskii, J.U. Reveles, D.R. Salahub, A. Vela, The deMon User's Guide, Version 1.1, www.deMon-software.com (2004)

P. Calaminici, R. Flores-Moreno, A.M. Köster, Structures and Vibrations of Nb₃O and Nb₃O^-: A Density Functional Study, J. Chem. Phys. 121, 3558 (2004)

A.M. Köster, J.U. Reveles, J.M. del Campo, Calculation of the Exchange-Correlation Potential with Auxiliary Function Densities, J. Chem. Phys. 121, 3417 (2004)

A.M. Köster, R. Flores-Moreno, J.U. Reveles, Efficient and Reliable Numerical Integration of Exchange-Correlation Energies and Potentials, J. Chem. Phys. 121, 681 (2004)

C. Quintanar, R. Caballero, A.M. Köster, Long-Range Interactions in Embedded Ionic Cluster Calculations, Int. J. Quantum Chem. 96, 483 (2004)

J.U. Reveles, A.M. Köster, Geometry Optimization in Density Functional Methods, J. Comput. Che. 25, 1109 (2004)

A.M. Köster, Hermite Gaussian Auxiliary Functions for the Variational Fitting of the Coulomb Potential in Density Functional Methods, J. Chem. Phys. 118, 9943 (2003)

P. Calaminici, A.M. Köster, D.R. Salahub, Negative Ion Photoelectron Spectra Simulation of V₃O from a Density Functional Study, J. Chem. Phys. 118, 4913 (2003)

A.M. Köster, A. Goursot, D.R. Salahub, deMon in Comprehensive Coordination Chemistry-II: From Biology to Nanotechnology, Vol. 2, Chapter 2.57, pp. 681, Editors: J. McCleverty, T.J. Meyer, B. Lever, Elsevier (2003)

P. Calaminici, A.M. Köster, Structures and Vibrations of V₃O and V₃O^-: A Density Functional Study, Int. J. Quantum Chem. 91, 317 (2003)

K. Jug, B. Zimmermann, A.M. Köster, Growth Pattern and Bonding of Copper Clusters, Int. J. Quantum Chem. 90, 594 (2002)

A.M. Köster, P. Calaminici, Z. Gómez, J.U. Reveles, Density Functional Calculation of Transition Metal Clusters in Reviews of Modern Quantum Chemistry, A Celebration of the Contribution of Robert G. Parr, Editor: K. Sen, World Scientific Publishing Co. (2002)

K. Jug, B. Zimmermann, P. Calaminici, A.M. Köster, Structure and Stability of Small Copper Cluster, J. Chem. Phys. 116, 4497 (2002)

P. Calaminici, A.M. Köster, K. Jug, C. Arbez-Gindre, C.G. Screttas, Mechanism for Large First Hyperpolarizabilities of Phosphonic Acid Stilbene Deivatives, J. Comput. Chem. 23, 291 (2002)

E. Sicilia, G. De Luca, S. Chiodo, N. Russo, P. Calaminici, A.M. Köster, K. Jug, Density Functional Theory Calculations of Nuclear Quadrupole Coupling Constants with Calibrated ¹⁴N Quadrupole Moments, Mol. Phys. 99, 1039 (2001)

K. Jug, F. Janetzko, A.M. Köster, Calculation of Heat Capacities and Entropies with Quantum Chemical Methods, J. Chem. Phys. 114, 5472 (2001)

P. Calaminici, A.M. Köster, T. Carrington Jr., P.N. Roy, N. Russo, D.R. Salahub, V₃: Structure and Vibration from Density Functional Theory, Franck-Condon Factors and the PFI-ZEKE Spectrum, J. Chem. Phys. 114, 4036 (2001)

A. Martínez, P. Calaminici, A.M. Köster, D.R. Salahub, Bonding in Nb₃O, Nb₃S, Nb₃Se: A Topological Analysis of the Electrostatic Potential, J. Chem. Phys. 114, 819 (2001)

H. Reis, M.G. Papadopoulos, P. Calaminici, K. Jug, A.M. Köster, Calculation of Macroscopic Linear and Nonlinear Optical Susceptibilities for the Naphthalene, Anthracene and meta-Nitroaniline Crystals, Chem. Phys. 261, 359 (2000)

G. Geudtner, K. Jug, A.M. Köster, Cu Adsorption on the MgO(100) Surface, Surf. Science 467, 98 (2000)

P. Calaminici, A.M. Köster, A. Vela, K. Jug, Comparison of Static Polarizabilities of Cu_n with Na_n and Li_n (n £ 9) Clusters, J. Chem. Phys. 113, 2199 (2000)

K. Jug, L. Kunert, A.M. Köster, Dipole Moments and Molecular Electrostatic Potentials from MSINDO, Theor. Chem. Acc. 104, 417 (2000)

P. Calaminici, K. Jug, A.M. Köster, V.E. Ingamells, M.G. Papadopoulos, Polarizabilities of Azabenzenes, J. Chem. Phys. 112, 6301 (2000)

A.M. Köster, P. Calaminici, A. Martínez, Reactions of Mo Atoms and Cations with NO: A Density Functional Study in Metal-Ligand Interactions in Chemistry, Physics and Biology, Editiors: N. Russo and D. Salahub, NATO Science Series Vol. 546, Kluwer Academic Publishers (2000)

G. De Luca, N. Russo, A.M. Köster, P. Calaminici, K. Jug, Density Functional Theory Calculations of Nuclear Quadrupole Coupling Constants with Calibrated ¹⁷O Quadrupole Moments, Mol. Phys. 97, 347 (1999)

M. Leboeuf, A.M. Köster, K. Jug, D.R. Salahub, Topological Analysis of the Molecular Electrostatic Potential, J. Chem. Phys. 111, 4893 (1999)

P. Calaminici, K. Jug, A.M. Köster, Static Polarizabilities of Na_n (n £ 9) Clusters: An all-electron Density Functional Study, J. Chem. Phys. 111, 4613 (1999)

A. Martínez, P. Calaminici, A.M. Köster, S. Mitchell, Interaction of Cr and Cr⁺ with NO: A Density Functional Study, Chem. Phys. Lett. 299, 630 (1999)

A.M. Köster, Entwicklung einer LCGTO-Dichtefunktionalmethode mit Hilfsfunktionen, Habilitation, Universität Hannover (1998)

P. Calaminici, K. Jug, A.M. Köster, Density Functional Calculations of Molecular Polarizabilities and Hyperpolarizabilities, J. Chem. Phys. 109, 7756 (1998)

G. Geudtner, A.M. Köster, K. Jug, SINDO1 Study of Diffusion in ß-LiAl, Ber. Bunsenges. Phys. Chem. 102, 833 (1998)

M. Krack, A.M. Köster, An Adaptive Numerical Integrator for Integrals, J. Chem. Phys. 108, 3226 (1998)

M. Leboeuf, A.M. Köster, D.R. Salahub, Approximation of Molecular Electrostatic Potentials in Density Functional Methods, Theor. Chem. Acc. 96, 23 (1997)

M. Krack, A.M. Köster, K.Jug, Approximated Molecular Electrostatic Potentials from Semiempirical Wavefunctions, J. Comput. Chem. 18, 301 (1997)

A. Martínez, A.M. Köster, D.R. Salahub, Reaction of a Mo Atom with H₂, N₂ and O₂: A Density Functional Study, J. Phys. Chem. A 101, 1532 (1997)

P. Calaminici, A.M. Köster, N. Russo, D.R. Salahub, A Density Functional Study of Small Copper Clusters Cu_n (n  £ 5), J. Chem. Phys. 105, 9546 (1996)

A.M. Köster, M. Leboeuf, D.R. Salahub, Molecular Electrostatic Potentials from Density Functional Theory in Theoretical and Computational Chemistry 3, Editors: J.S. Murray and K. Sen, Elsevier (1996)

A.M. Köster, P. Calaminici, N. Russo, Nuclear Quadrupole Coupling Constants from Density Functional Calculations, Phys. Rev. A 53, 3865 (1996)

A.M. Köster, Efficient Recursive Computation of Molecular Integrals for Density Functional Methods, J. Chem. Phys. 104, 4114 (1996)

J. Guan, M.E. Casida, A.M. Köster, D.R. Salahub, All-Electron Local and Gradient-Corrected Density-Functional Calculations of Na_n Dipole Polarizabilities for n = 1-6, Phys. Rev. B 52, 2184 (1995)

S. Behrens, A.M. Köster, K. Jug, Delocalization Energy of p Electrons as an Index for Aromaticity of Condensed Polycyclic Hydrocarbons, J. Org. Chem. 59, 2546 (1994)

K. Jug, M. Matuschewski, A.M. Köster, s-p Energy Diagrams for Substituted Rings, J. Phys. Org. Chem. 6, 645 (1993)

A.M. Köster, K. Jug, Multipole Moment Analysis for Hydrides, Fluorides and Lithium Compounds of First- and Second-Row Elements, Int. J. Quantum Chem. 48, 295 (1993)

A.M. Köster, C. Kölle, K. Jug, Approximation of Molecular Electrostatic Potentials, J. Chem. Phys. 99, 1224 (1993)

R.F. Nalewajski, A.M. Köster, T. Bredow, K. Jug, Charge Sensitivity Analysis of Oxide Catalysts: TiO₂ (110) and (100) Surface Model Clusters and H₂O Adsorption, J. Mol. Catal. 82, 407 (1993)

R.F. Nalewajski, A.M. Köster, K. Jug, Chemical Valence from the Two-Particle Density Matrix, Theor. Chim. Acta 85, 463 (1993)

A.M. Köster, Reaktivitätskriterien aus Ladungsanalysen, Dissertation, Universität Hannover (1992)

K. Jug, A.M. Köster, Nonsymmetrical Orthogonalization as a Consequence of Charge and Moment Conservation, Chem. Phys. Lett. 192, 437 (1992)

K. Jug, E. Fasold, A.M. Köster, Charge and Valence in Lithium Compounds, Chem. Phys. Lett. 188, 294 (1992)

K. Jug, A.M. Köster, Aromaticity as Multidimensional Phenomenon, J. Phys. Org. Chem. 4, 163 (1991)

K. Jug, A.M. Köster, A Valence and Charge Criterion for Reactivity of p Electron Systems, J. Phys. Org. Chem. 3, 599 (1990)

K. Jug, A.M. Köster, Influence of s and p Electrons on Aromaticity, J. Am. Chem. Soc. 112, 6772 (1990)

A.M. Köster, Untersuchung von Aromatizitätskriterien, Diplomarbeit, Universität Hannover (1989)

Research Topics

The current research activities of our group are in the further algorithmic development of ADFT and ADPT as well as in their application to cluster science. In this respect ADFT Born-Oppenheimer molecular dynamics (BOMD) simulations are of particular interest. With the rise of nanoscience the melting of finite systems has attracted considerable attention. Although, experiments for the determination of finite system melting exist [1], their applications are limited, e.g. to size selected metal clusters with relative low melting temperatures. Therefore, theoretical simulations are of great importance. Today, it is common knowledge that the reliable prediction of finite system melting requires first-principle BOMD simulations. With such simulations melting temperatures can be predicted within 50 K or better with respect to experimental results. We use ADFT BOMD simulations to study the melting of size selected clusters [2]. This approach benefits from new parallel MD implementations in deMon2k like the parallel tempering approach (see Fig. 4) [3]. The ADFT BOMD approach in deMon2k is also well suited for the study of the temperature dependency of molecular properties [4]. We also have used it for global structure optimizations [5,6] for which we now explore machine learning algorithms [7].

Figure 4: Schematics of the parallel tempering MD algorithm.

In order to improve the reliability of ADFT simulations, we constantly upgrade the ADFT methodology implemented in deMon2k. With the development and implementation of the variational Fock potential fitting global [8] and range-separated [9] hybrid functionals are now available in deMon2k for ADFT calculations. In a combined experimental-theoretical study [10] we have shown that ADFT hybrid functional calculations yield optimized structure parameters of similar accuracy as corresponding crystal structure analyses. Hybrid functionals are also essential for the quantitative calculation of activation energies of chemical reactions as a systematic study of pericyclic reactions showed (see Fig. 5) [11].

Figure 5: B3LYP/6-31G*/GEN-A2* reaction profiles for pericyclic reactions

With corresponding composite approaches that combine ADFT single-point energy hybrid calculations with structure optimizations employing the generalized gradient approximation accurate relative energies ([endif]--> 1 kcal/mol) for systems with more than 100 atoms become available [12].

For the study of nanocatalysis in complex environments, we aim for QM/MM free energy gradient calculations. To this end, we are implementing an integrated QM/MM module in deMon2k as depicted in Fig. 6 [13]. This figure shows that from the gradient calculation on, QM and MM atoms are treated on an equal footing in deMon2k. Thus, the following utility modules for structure optimization and chemical reaction modeling as well as for molecular dynamics simulation are the same for QM, MM and QM/MM calculations. On the other hand, the analytic higher-order SCF energy derivatives calculated in the TD-ADFT and ADPT modules of Fig. 6 are directly linked to the ADFT module and, therefore, are only available for the QM part of a QM/MM calculation. The QM/MM frequency analysis is linked to both the ADPT and MM module.

Figure 6: Diagram of deMon2k energy modules for QM/MM calculations and their relation to gradient and property calculations.

As a first application, we calculated the TD-ADFT visible spectrum of Reichardt’s dye at the PBE/DZVP-GGA/GEN-A2* level as shown in Fig. 7. For these calculations the molecular structures were optimized in vacuum, water, methanol and ethanol. All solvent molecules where calculated at the MM level, accounting for a total of around 1500 atoms. The OPLS-AA force field was used in all QM/MM calculations. As Fig. 7 shows, the experimentally observed solvent shifts in the excitation spectra are reproduced qualitatively correctly by our QM/MM calculations.

Figure 7: Calculated Reichardt’s dye spectra in vacuum (black dashed line), water (black solid line), methanol (red line).and ethanol (violet line). Solutions of the molecule in water, methanol and ethanol is shown in the top right insert.

References

[1] M. Schmidt, R. Kusche, B. von Issendorff, H. Haberland, Nature 393, 238 (1998).

[2] J.M. Vásquez-Pérez, G.U. Gamboa, D. Mejía-Rodríguez, A. Alvarez-Ibarra, G. Geudtner, P. Calaminici, A.M. Köster, J. Phys. Chem. Lett. 6, 4646 (2015).

[3] F. Louisnard, G. Geudnter, A.M. Köster, J. Cuny, Theor. Chem. Acc. 140, 95 (2021).

[4] G.U. Gamboa, P. Calaminici, G. Geudtner, A.M. Köster, J. Phys. Chem. A 112, 11969 (2008).

[5] A.M. Köster, P. Calaminici, E. Orgaz, D.R. Roy, J.U. Reveles, S.N. Khanna, J. Am. Chem. Soc. 133, 12192 (2011).

[6] V.M. Medel, A.C. Reber, V. Chauhan, P. Sen, A.M. Köster, P. Calaminici, S.N. Khanna, J. Am. Chem. Soc. 136, 8229 (2014).

[7] M.P. Lourenço, L. Barrios Herrera, J. Hostaš, P. Calaminici, A.M. Köster, A. Tchagang, D.R. Salahub, Theor. Chem. Acc. 140, 116 (2021).

[8] D. Mejía-Rodríguez, X. Huang, J.M. del Campo, A.M. Köster, Hybrid Functionals with Variationally Fitted Exact Exchange, Adv. Quantum Chem. 71, 41 (2015).

[9] J.N. Pedroza-Montero, F.A. Delesma, J.L. Morales, P. Calaminici, A.M. Köster, Variational Fitting of the Fock Exchange Potential with Modified Cholesky Decomposition, J. Chem. Phys. 153, 134112 (2020).

[10] M. Böning, K. Dongol, G. Romero Boston, S. Schmitz, R. Wartchow, J. Samaniego-Rojas, A.M. Köster, H. Butenschön, Trifluoromethyl Substituted Benzocyclobutenone and Benzocyclobutenedione: The Structure Anomaly of (Benzocyclobutenedione)tricarbonyl-chromium Complexes, Organometallics 38, 3039 (2019).

[11] J.R. Gómez-Pérez, F.A. Delesma, P. Calaminici, A.M. Köster, Accuracy of auxiliary density functional theory hybrid calculations for activation and reaction enthalpies of pericyclic reactions, J. Mol. Modeling 24, 223 (2018).

[12] S.E. Pérez-Figueroa, P. Calaminici, A.M. Köster, A Hybrid ADFT Study of the C104 and C106 IPR Isomers, J. Phys. Chem. A 123, 4565 (2019).

[13]     J.D. Samaniego-Rojas, L.-I. Hernández-Segura, L. López-Sosa, R.I. Delgado-Venegas, B. Gomez, J.-C. Lambry, A. de la Lande, T. Mineva, J. Alejandre, B.A. Zúñiga-Gutiérrez, R. Flores-Moreno, P. Calaminici, G. Geudtner, A.M. Köster, QM/MM with Auxiliary DFT in deMon2k, in Multiscale Dynamics Simulations: Nano- and Nano-bio Systems in Complex Environments, Editors: D.R. Salahub, D. Wei, RSC Theoretical and Computational Chemistry Series, London in press.

Courses

Theoretical Chemistry I
This course introduces first-principles self-consistent field (SCF) electronic structure methods. To this end, the molecular Hartree-Fock and Kohn-Sham methods are derived in the framework of the linear combination of atomic orbital (LCAO) approximation. Special attention is given to the efficient calculation of molecular integrals by density fitting. The Kohn-Sham method is further elaborated in order to derive auxiliary density functional theory (ADFT). Based on the ADFT energy expression the calculation of first- and second-order LCAO energy derivatives is discussed.

The aim of the course is to prepare students for their independent theoretical work on modern electronic structure methods. Course participants should have elementary knowledge of one-particle quantum systems and linear algebra.

Table of contents:

1. Born-Oppenheimer Approximation
2. Atomic Units
3. The Antisymmetry Principle
4. The MO-LCAO Approximation
5. The Molecular Hartree-Fock Method
6. Variational Fitting of Coulomb and Fock Potentials
7. The Molecular Kohn-Sham Method
8. Auxiliary Density Functional Theory (ADFT)
9. ADFT Gradient Calculation
10. Auxiliary Density Perturbation Theory (ADPT)
11. Second Analytic ADFT Derivatives

Suggested Literature:

• F.L. Pilar, Elementary Quantum Chemistry, 2nd Edition (McGraw-Hill, New York, 1990)
• A. Szabo, N .S. Ostlund, Modern Quantum Chemistry (Dover Publications, New York, 1996)
• T. Helgaker, P. Jorgensen, J. Olsen, Molecular Electronic Structure Theory (Wiley, New York, 2000)

Computational Chemistry

This  course  is  a  practical  introduction  to  Computational  Chemistry  with  the  focus  on  first-principles electronic structure  methods,  in  particular  density  functional  theory  (DFT)  methods.  In the first  part  of  the course  the  students  are  familiarized  with  LINUX  and  UNIX  based  operating  systems  and  the common  input structures  used  in  Computational  Chemistry.  The second part  of  the  course  are practical  exercises  for  single  point  energy  calculations,  structure  optimizations  and  molecular property  calculations  on  simple  systems.  The  course finishes  with a computational project of around 6 weeks  in  which  the  students  demonstrate  their  capability  to  plan  and  realize  the  simulation  of  a “real life” problem. All calculations are performed with the LCGTO-DFT program deMon2k on state-of-the art LINUX clusters. 

Table of contents:

• Introduction to LINUX and UNIX
• Introduction to deMon2k
• Cartesian, Z-Matrix and Mixed inputs
• Basis Sets and Pseudopotentials
• Single Point Energy Calculations
• Structure Optimization and Frequency Analysis
• Molecular Property Calculations
• QM/MM Calculations
• Computational Project

Seminars

• Force Field Methods
• Semiempirical Methods
• Density Functional Theory Methods
• Ab-Initio Methods

Suggested Literature:

deMon2k online manual
www.demon-software.com