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Christof Hättig

Bio: Christof Hättig is an academic researcher from Ruhr University Bochum. The author has contributed to research in topics: Coupled cluster & Excited state. The author has an hindex of 56, co-authored 191 publications receiving 15284 citations. Previous affiliations of Christof Hättig include University of Bonn & Aarhus University.


Papers
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TL;DR: In this article, the second-order Moller-Plesset perturbation theory (MP2) correlation energy with the cardinal number X is investigated for the correlation consistent basis-set series cc-pVXZ and cc-PV(X+d)Z.
Abstract: The convergence of the second-order Moller–Plesset perturbation theory (MP2) correlation energy with the cardinal number X is investigated for the correlation consistent basis-set series cc-pVXZ and cc-pV(X+d)Z. For the aug-cc-pVXZ and aug-cc-pV(X+d)Z series the convergence of the MP2 correlation contribution to the dipole moment is studied. It is found that, when d-shell electrons cannot be frozen, the cc-pVXZ and aug-cc-pVXZ basis sets converge much slower for third-row elements then they do for first- and second-row elements. Based on the results of these studies criteria are deduced for the accuracy of auxiliary basis sets used in the resolution of the identity (RI) approximation for electron repulsion integrals. Optimized auxiliary basis sets for RI-MP2 calculations fulfilling these criteria are reported for the sets cc-pVXZ, cc-pV(X+d)Z, aug-cc-pVXZ, and aug-cc-pV(X+d)Z with X=D, T, and Q. For all basis sets the RI error in the MP2 correlation energy is more than two orders of magnitude smaller than...

1,660 citations

Journal ArticleDOI
TL;DR: A new implementation of the approximate coupled cluster singles and doubles method CC2 is reported, which is suitable for large scale integral-direct calculations and employs the resolution of the identity (RI) approximation for two-electron integrals to reduce the CPU time needed for calculation and I/O of these integrals.
Abstract: A new implementation of the approximate coupled cluster singles and doubles method CC2 is reported, which is suitable for large scale integral-direct calculations. It employs the resolution of the identity (RI) approximation for two-electron integrals to reduce the CPU time needed for calculation and I/O of these integrals. We use a partitioned form of the CC2 equations which eliminates the need to store double excitation cluster amplitudes. In combination with the RI approximation this formulation of the CC2 equations leads to a reduced scaling of memory and disk space requirements with the number of correlated electrons (n) and basis functions (N) to, respectively, O(N2) and O(nN2), compared to O(n2N2) in previous implementations. The reduced CPU, memory and disk space requirements make it possible to perform CC2 calculations with accurate basis sets on large molecules, which would not be accessible with conventional implementations of the CC2 method. We present an application to vertical excitation ene...

1,326 citations

Journal ArticleDOI
Kestutis Aidas1, Celestino Angeli2, Keld L. Bak3, Vebjørn Bakken4, Radovan Bast5, Linus Boman6, Ove Christiansen3, Renzo Cimiraglia2, Sonja Coriani7, Pål Dahle8, Erik K. Dalskov, Ulf Ekström4, Thomas Enevoldsen9, Janus J. Eriksen3, Patrick Ettenhuber3, Berta Fernández10, Lara Ferrighi, Heike Fliegl4, Luca Frediani, Kasper Hald11, Asger Halkier, Christof Hättig12, Hanne Heiberg13, Trygve Helgaker4, Alf C. Hennum14, Hinne Hettema15, Eirik Hjertenæs16, Stine Høst3, Ida-Marie Høyvik3, Maria Francesca Iozzi17, Brannislav Jansik18, Hans-Jørgen Aa. Jensen9, Dan Jonsson, Poul Jørgensen3, Johanna Kauczor19, Sheela Kirpekar, Thomas Kjærgaard3, Wim Klopper20, Stefan Knecht21, Rika Kobayashi22, Henrik Koch16, Jacob Kongsted9, Andreas Krapp, Kasper Kristensen3, Andrea Ligabue23, Ola B. Lutnæs24, Juan Ignacio Melo25, Kurt V. Mikkelsen26, Rolf H. Myhre16, Christian Neiss27, Christian B. Nielsen, Patrick Norman19, Jeppe Olsen3, Jógvan Magnus Haugaard Olsen9, Anders Osted, Martin J. Packer9, Filip Pawłowski28, Thomas Bondo Pedersen4, Patricio Federico Provasi29, Simen Reine4, Zilvinas Rinkevicius5, Torgeir A. Ruden, Kenneth Ruud, Vladimir V. Rybkin20, Paweł Sałek, Claire C. M. Samson20, Alfredo Sánchez de Merás30, Trond Saue31, Stephan P. A. Sauer26, Bernd Schimmelpfennig20, Kristian Sneskov11, Arnfinn Hykkerud Steindal, Kristian O. Sylvester-Hvid, Peter R. Taylor32, Andrew M. Teale33, Erik I. Tellgren4, David P. Tew34, Andreas J. Thorvaldsen3, Lea Thøgersen35, Olav Vahtras5, Mark A. Watson36, David J. D. Wilson37, Marcin Ziółkowski38, Hans Ågren5 
TL;DR: Dalton is a powerful general‐purpose program system for the study of molecular electronic structure at the Hartree–Fock, Kohn–Sham, multiconfigurational self‐consistent‐field, Møller–Plesset, configuration‐interaction, and coupled‐cluster levels of theory.
Abstract: Dalton is a powerful general-purpose program system for the study of molecular electronic structure at the Hartree-Fock, Kohn-Sham, multiconfigurational self-consistent-field, MOller-Plesset, confi ...

1,212 citations

Journal ArticleDOI
TL;DR: In this paper, an implementation of analytic basis set gradients is reported for the optimization of auxiliary basis sets in resolution-of-the-identity second-order Moller-Plesset perturbation theory (RI-MP2) and approximate coupled-cluster singles-and-doubles (CC2) calculations.
Abstract: An implementation of analytic basis set gradients is reported for the optimization of auxiliary basis sets in resolution-of-the-identity second-order Moller–Plesset perturbation theory (RI-MP2) and approximate coupled-cluster singles-and-doubles (RI-CC2) calculations. The analytic basis set gradients are applied in the optimization of auxiliary basis sets for a number of large one-electron orbital basis sets which provide correlation energies close to the basis set limit: the core–valence basis sets cc-pwCVXZ (B–Ne, Al–Ar) with X = D, T, Q, 5, the quintuple-ζ basis sets cc-pV5Z (H–Ar) and cc-pV(5 + d)Z (Al–Ar) and the doubly-polarized valence quadruple-ζ basis sets QZVPP for Li–Kr. The quality of the optimized auxiliary basis sets is evaluated for several test sets with small and medium sized molecules.

636 citations


Cited by
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TL;DR: The revised DFT-D method is proposed as a general tool for the computation of the dispersion energy in molecules and solids of any kind with DFT and related (low-cost) electronic structure methods for large systems.
Abstract: The method of dispersion correction as an add-on to standard Kohn-Sham density functional theory (DFT-D) has been refined regarding higher accuracy, broader range of applicability, and less empiricism. The main new ingredients are atom-pairwise specific dispersion coefficients and cutoff radii that are both computed from first principles. The coefficients for new eighth-order dispersion terms are computed using established recursion relations. System (geometry) dependent information is used for the first time in a DFT-D type approach by employing the new concept of fractional coordination numbers (CN). They are used to interpolate between dispersion coefficients of atoms in different chemical environments. The method only requires adjustment of two global parameters for each density functional, is asymptotically exact for a gas of weakly interacting neutral atoms, and easily allows the computation of atomic forces. Three-body nonadditivity terms are considered. The method has been assessed on standard benchmark sets for inter- and intramolecular noncovalent interactions with a particular emphasis on a consistent description of light and heavy element systems. The mean absolute deviations for the S22 benchmark set of noncovalent interactions for 11 standard density functionals decrease by 15%-40% compared to the previous (already accurate) DFT-D version. Spectacular improvements are found for a tripeptide-folding model and all tested metallic systems. The rectification of the long-range behavior and the use of more accurate C(6) coefficients also lead to a much better description of large (infinite) systems as shown for graphene sheets and the adsorption of benzene on an Ag(111) surface. For graphene it is found that the inclusion of three-body terms substantially (by about 10%) weakens the interlayer binding. We propose the revised DFT-D method as a general tool for the computation of the dispersion energy in molecules and solids of any kind with DFT and related (low-cost) electronic structure methods for large systems.

32,589 citations

01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

Journal ArticleDOI
TL;DR: It is shown by an extensive benchmark on molecular energy data that the mathematical form of the damping function in DFT‐D methods has only a minor impact on the quality of the results and BJ‐damping seems to provide a physically correct short‐range behavior of correlation/dispersion even with unmodified standard functionals.
Abstract: It is shown by an extensive benchmark on molecular energy data that the mathematical form of the damping function in DFT-D methods has only a minor impact on the quality of the results. For 12 different functionals, a standard "zero-damping" formula and rational damping to finite values for small interatomic distances according to Becke and Johnson (BJ-damping) has been tested. The same (DFT-D3) scheme for the computation of the dispersion coefficients is used. The BJ-damping requires one fit parameter more for each functional (three instead of two) but has the advantage of avoiding repulsive interatomic forces at shorter distances. With BJ-damping better results for nonbonded distances and more clear effects of intramolecular dispersion in four representative molecular structures are found. For the noncovalently-bonded structures in the S22 set, both schemes lead to very similar intermolecular distances. For noncovalent interaction energies BJ-damping performs slightly better but both variants can be recommended in general. The exception to this is Hartree-Fock that can be recommended only in the BJ-variant and which is then close to the accuracy of corrected GGAs for non-covalent interactions. According to the thermodynamic benchmarks BJ-damping is more accurate especially for medium-range electron correlation problems and only small and practically insignificant double-counting effects are observed. It seems to provide a physically correct short-range behavior of correlation/dispersion even with unmodified standard functionals. In any case, the differences between the two methods are much smaller than the overall dispersion effect and often also smaller than the influence of the underlying density functional.

14,151 citations

Journal ArticleDOI
TL;DR: This paper presents a meta-modelling procedure called "Continuum Methods within MD and MC Simulations 3072", which automates the very labor-intensive and therefore time-heavy and expensive process of integrating discrete and continuous components into a discrete-time model.
Abstract: 6.2.2. Definition of Effective Properties 3064 6.3. Response Properties to Magnetic Fields 3066 6.3.1. Nuclear Shielding 3066 6.3.2. Indirect Spin−Spin Coupling 3067 6.3.3. EPR Parameters 3068 6.4. Properties of Chiral Systems 3069 6.4.1. Electronic Circular Dichroism (ECD) 3069 6.4.2. Optical Rotation (OR) 3069 6.4.3. VCD and VROA 3070 7. Continuum and Discrete Models 3071 7.1. Continuum Methods within MD and MC Simulations 3072

13,286 citations