Jens Antony

Bio: Jens Antony is an academic researcher from University of Münster. The author has contributed to research in topics: Density functional theory & Interaction energy. The author has an hindex of 20, co-authored 26 publications receiving 25002 citations. Previous affiliations of Jens Antony include University of Lübeck & Free University of Berlin.

A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu

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.

Density functional theory with dispersion corrections for supramolecular structures, aggregates, and complexes of (bio)organic molecules.

Abstract: Kohn–Sham density functional theory (KS-DFT) is nowadays the most widely used quantum chemical method for electronic structure calculations in chemistry and physics. Its further application in e.g. supramolecular chemistry or biochemistry has mainly been hampered by the inability of almost all current density functionals to describe the ubiquitous attractive long-range van der Waals (dispersion) interactions. We review here methods to overcome this defect, and describe in detail a very successful correction that is based on damped –C6·R–6 potentials (DFT-D). As examples we consider the non-covalent inter- and intra-molecular interactions in unsaturated organic molecules (so-called π–π stacking in benzenes and dyes), in biologically relevant systems (nucleic acid bases/pairs, proteins, and ‘folding’ models), between fluorinated molecules, between curved aromatics (corannulene and carbon nanotubes) and small molecules, and for the encapsulation of methane in water clusters. In selected cases we partition the interaction energies into the most relevant contributions from exchange-repulsion, electrostatics, and dispersion in order to provide qualitative insight into the binding character.

Density functional theory including dispersion corrections for intermolecular interactions in a large benchmark set of biologically relevant molecules

Abstract: Density functional theory including dispersion corrections (DFT-D) is applied to calculate intermolecular interaction energies in an extensive benchmark set consisting mainly of DNA base pairs and amino acid pairs, for which CCSD(T) complete basis set limit estimates are available (JSCH-2005 database). The three generalized gradient approximation (GGA) density functionals B-LYP, PBE and the new B97-D are tested together with the popular hybrid functional B3-LYP. The DFT-D interaction energies deviate on average by less than 1 kcal mol−1 or 10% from the reference values. In only six out of 161 cases, the deviation exceeds 2 kcal mol−1. With one exception, the few larger deviations occur for non-equilibrium structures extracted from experimental geometries. The largest absolute deviations are observed for pairs of oppositely charged amino acids which are, however, not significant on a relative basis due to the huge interaction energies >100 kcal mol−1 involved. The counterpoise (CP) correction for the basis set superposition error with the applied triple-zeta AO basis sets varies between 0 and −1 kcal mol−1 (<5% of the interaction energy in most cases) except for four complexes, where it is up to −1.4 kcal mol−1. It is thus suggested to skip the laborious calculation of the CP correction in DFT-D treatments with reasonable basis sets. The three dispersion corrected GGAs considered differ mainly for the interactions of the hydrogen-bonded DNA base pairs, which are systematically too small by 0.6 kcal mol−1 in case of B97-D, while for PBE-D they are too high by 1.5 kcal mol−1, and for B-LYP-D by 0.5 kcal mol−1. The all in all excellent results that have been obtained at affordable computational costs suggest the DFT-D method to be a routine tool for many applications in organic chemistry or biochemistry.

Structures and interaction energies of stacked graphene–nucleobase complexes

Abstract: The noncovalent interactions of nucleobases and hydrogen-bonded (Watson–Crick) base-pairs on graphene are investigated with the DFT-D method, i.e., all-electron density functional theory (DFT) in generalized gradient approximation (GGA) combined with an empirical correction for dispersion (van der Waals) interactions. Full geometry optimization is performed for complexes with graphene sheet models of increasing size (up to C150H30). Large Gaussian basis sets of at least polarized triple-ζ quality are employed. The interaction energies are extrapolated to infinite lateral size of the sheets. Comparisons are made with B2PLYP-D and SCS-MP2 single point energies for coronene and C54H18 substrates. The contributions to the binding (Pauli exchange repulsion, electrostatic and induction, dispersion) are analyzed. At a frozen inter-fragment distance, the interaction energy surface of the rigid C96H24 and base monomers is explored in three dimensions (two lateral and one rotational). Methodologically and also regarding the results of an energy decomposition analysis, the complexes behave like other π-stacked systems examined previously. The sequence obtained for the interaction energy of bases with graphene (G > A > T > C > U) is the same for all methods and supports recent experimental findings. The absolute values are rather large (about −20 to −25 kcal mol−1) but in the expected range for π-systems of that size. The relatively short equilibrium inter-plane distance (about 3 A) is consistent with atomic force microscopy results of monolayer guanine and adenine on graphite. In graphene⋯Watson–Crick pair complexes, the bases lie differently from their isolated energy minima leading to geometrical anti-cooperativity. Together with an electronic contribution of 2 and 6%, this adds up to total binding anti-cooperativities of 7 and 12% for AT and CG, respectively, on C96H24. Hydrogen bonds themselves are merely affected by binding on graphene.

Noncovalent Interactions between Graphene Sheets and in Multishell (Hyper)Fullerenes

Abstract: The intershell and interlayer interaction (complexation) energies of C60 inside C240 (C60@C240) and of graphene sheets are investigated by all-electron density functional theory (DFT) using generalized gradient approximation (GGA) functionals and a previously developed empirical correction for dispersion (van der Waals) effects (DFT−D method). Large Gaussian basis sets of polarized triple-ζ quality that provide very small basis set superposition errors (<10% of ΔE) are employed. The theoretical approach is first applied to graphene sheet model dimers of increasing size (up to (C216H36)2). The interaction energies are extrapolated to infinite lateral size of the sheets. The value of −66 meV/atom obtained for the interaction energy of two sheets supports the most recent experimental estimate for the exfoliation energy of graphite (−52 ± 5 meV/atom). The interlayer equilibrium distance (334 ± 3 pm) is also obtained accurately. The binding energy of C60 inside C240 is calculated to be −184 kcal mol-1 which is...

A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu

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.

Effect of the damping function in dispersion corrected density functional theory

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.

Long-range corrected hybrid density functionals with damped atom–atom dispersion corrections

Abstract: We report re-optimization of a recently proposed long-range corrected (LC) hybrid density functional [J.-D. Chai and M. Head-Gordon, J. Chem. Phys., 2008, 128, 084106] to include empirical atom–atom dispersion corrections. The resulting functional, ωB97X-D yields satisfactory accuracy for thermochemistry, kinetics, and non-covalent interactions. Tests show that for non-covalent systems, ωB97X-D shows slight improvement over other empirical dispersion-corrected density functionals, while for covalent systems and kinetics it performs noticeably better. Relative to our previous functionals, such as ωB97X, the new functional is significantly superior for non-bonded interactions, and very similar in performance for bonded interactions.

Long-Range Corrected Hybrid Density Functionals with Damped Atom-Atom Dispersion Corrections

Abstract: Long-Range Corrected Hybrid Density Functionals with Damped Atom-Atom Dispersion Corrections Jeng-Da Chai ∗ and Martin Head-Gordon † Department of Chemistry, University of California and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA (Dated: June 14, 2008) We report re-optimization of a recently proposed long-range corrected (LC) hybrid density func- tionals [J.-D. Chai and M. Head-Gordon, J. Chem. Phys. 128, 084106 (2008)] to include empirical atom-atom dispersion corrections. The resulting functional, ωB97X-D yields satisfactory accuracy for thermochemistry, kinetics, and non-covalent interactions. Tests show that for non-covalent sys- tems, ωB97X-D shows slight improvement over other empirical dispersion-corrected density func- tionals, while for covalent systems and kinetics, it performs noticeably better. Relative to our previous functionals, such as ωB97X, the new functional is significantly superior for non-bonded interactions, and very similar in performance for bonded interactions. I. INTRODUCTION Due to its favorable cost-to-performance ratio, Kohn- Sham density-functional theory (KS-DFT) [1, 2] has be- come the most popular electronic structure theory for large-scale ground-state systems [3–5]. Its extension for treating excited-state systems [6, 7], time-dependent den- sity functional theory (TDDFT), has also been developed to the stage where it is now very widely used. The essential ingredient of KS-DFT, the exchange- correlation energy functional E xc , remains unknown and needs to be approximated. Semi-local gradient-corrected density functionals, though successful in many applica- tions, lead to qualitative failures in some circumstances, where the accurate treatment of non-locality of exchange- correlation hole becomes crucial. These situations occur mostly in the asymptotic regions of molecular systems, such as spurious self-interaction effects upon dissociation [8, 9] and dramatic failures for long-range charge-transfer excitations [10–12]. Widely used hybrid density function- als, like B3LYP [13, 14], do not qualitatively resolve these problems. These self-interaction errors can be qualitatively re- solved using the long-range corrected (LC) hybrid density functionals [15, 16, 18], which employ 100% Hartree-Fock (HF) exchange for long-range electron-electron interac- tions. This is accomplished by a partition of unity, using erf(ωr)/r for long-range (treated by HF exchange) and erfc(ωr)/r for short-range (treated by an exchange func- tional), with the parameter ω controlling the partition- ing. Over the past five years, the LC hybrid scheme has been attracting increasing attention [15] since its compu- tational cost is comparable with standard hybrid func- tionals [13]. However, LC functionals have tended to be inferior to the best hybrids for properties such as ther- mochemistry. ∗ Electronic † Author address: jdchai@berkeley.edu to whom correspondence should be addressed. Electronic address: mhg@cchem.berkeley.edu Recently we have improved the overall accuracy at- tainable with the LC functionals by using a systematic optimization procedure [18]. One important conclusion is that optimizing LC and hybrid functionals with identical numbers of parameters in their GGA exchange and cor- relation terms leads to noticeably better results for all properties using the LC form. The resulting LC func- tional is called ωB97. Further statistically significant improvement results from re-optimizing the entire func- tional with one extra parameter corresponding to an ad- justable fraction of short-range exact exchange, defining the ωB97X functional. Independent test sets covering thermochemistry and non-covalent interactions support these conclusions. However, problems associated with the lack of non-locality of the correlation hole, such as the lack of dispersion interactions (London forces), still remain, as the semi-local correlation functionals cannot capture long-range correlation effects [19, 20]. There have been significant efforts to develop a frame- work that can account for long-range dispersion effects within DFT. Zaremba and Kohn (ZK) [21] derived an exact expression for the second-order dispersion energy in terms of the exact density-density response functions of the two separate systems. To obtain a tractable non- local dispersion functional, Dobson and Dinite (DD) [22] made local density approximations to the ZK response functions. DD’s non-local correlation functional was ob- tained independently [23] by modifying the effective den- sity defined in the earlier work of Rapcewicz and Ashcroft Starting from the formally exact expression of KS- DFT, the adiabatic connection fluctuation-dissipation theorem (ACFDT), for the ground-state exchange- correlation energy, Langreth and co-workers [25] devel- oped a so-called van der Waals density functional (vdW- DF) by making a series of reasonable approximations to yield a computationally tractable scheme. Recently, Becke and Johnson (BJ) developed a series of post-HF correlation models with a novel treatment for dispersion interactions based on the exchange-hole dipole moment [26]. The origin of dispersion claimed in the BJ models was recently questioned by Alonso, and A.

Advanced capabilities for materials modelling with Quantum ESPRESSO.

Abstract: Quantum ESPRESSO is an integrated suite of open-source computer codes for quantum simulations of materials using state-of-the-art electronic-structure techniques, based on density-functional theory, density-functional perturbation theory, and many-body perturbation theory, within the plane-wave pseudopotential and projector-augmented-wave approaches Quantum ESPRESSO owes its popularity to the wide variety of properties and processes it allows to simulate, to its performance on an increasingly broad array of hardware architectures, and to a community of researchers that rely on its capabilities as a core open-source development platform to implement their ideas In this paper we describe recent extensions and improvements, covering new methodologies and property calculators, improved parallelization, code modularization, and extended interoperability both within the distribution and with external software