The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
John P Perdew - One of the best experts on this subject based on the ideXlab platform.
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accurate and numerically efficient r 2 scan meta Generalized Gradient approximation
Bulletin of the American Physical Society, 2021Co-Authors: James W Furness, John P Perdew, Aaron D Kaplan, Jinliang Ning, Jianwei SunAbstract:The recently proposed rSCAN functional [J. Chem. Phys. 150, 161101 (2019)] is a regularized form of the SCAN functional [Phys. Rev. Lett. 115, 036402 (2015)] that improves SCAN's numerical performance at the expense of breaking constraints known from the exact exchange-correlation functional. We construct a new meta-Generalized Gradient approximation by restoring exact constraint adherence to rSCAN. The resulting functional maintains rSCAN's numerical performance while restoring the transferable accuracy of SCAN.
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Rehabilitation of the Perdew-Burke-Ernzerhof Generalized Gradient approximation for layered materials
Physical Review B, 2017Co-Authors: Haowei Peng, John P PerdewAbstract:The structural and energetic properties of layered materials present a challenge to density functional theory with common semilocal approximations to the exchange-correlation energy. By combining the most widely used semilocal Generalized Gradient approximation (GGA), the Perdew-Burke-Ernzerhof (PBE) one, with the revised Vydrov--van Voorhis nonlocal correlation functional (rVV10), both excellent structural and energetic properties of 28 layered materials have been recovered with a judicious parameter selection. We term the resulting functional PBE+rVV10L, with the ``L'' indicating that it is for layered materials. Such a combination is not new, and only involves refitting a single global parameter. However, the resulting excellent accuracy suggests such a dispersion-corrected PBE for many aspects of theoretical studies on layered materials. For comparison, we also present the results for PBE+rVV10 where the parameter is determined by 22 interaction energies between molecules.
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more realistic band gaps from meta Generalized Gradient approximations only in a Generalized kohn sham scheme
Physical Review B, 2016Co-Authors: Zenghui Yang, Jianwei Sun, Haowei Peng, John P PerdewAbstract:Unlike the local density approximation (LDA) and the Generalized Gradient approximation (GGA), calculations with meta-Generalized Gradient approximations (meta-GGA) are usually done according to the Generalized Kohn-Sham (gKS) formalism. The exchange-correlation potential of the gKS equation is nonmultiplicative, which prevents systematic comparison of meta-GGA band structures to those of the LDA and the GGA. We implement the optimized effective potential (OEP) of the meta-GGA for periodic systems, which allows us to carry out meta-GGA calculations in the same KS manner as for the LDA and the GGA. We apply the OEP to several meta-GGAs, including the new SCAN functional [Phys. Rev. Lett. 115, 036402 (2015)]. We find that the KS gaps and KS band structures of meta-GGAs are close to those of GGAs. They are smaller than the more realistic gKS gaps of meta-GGAs, but probably close to the less-realistic gaps in the band structure of the exact KS potential, as can be seen by comparing with the gaps of the EXX+RPA OEP potential. The well-known grid sensitivity of meta-GGAs is much more severe in OEP calculations.
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improved band gaps from meta Generalized Gradient approximations only in a Generalized kohn sham scheme
arXiv: Materials Science, 2016Co-Authors: Zenghui Yang, Jianwei Sun, Haowei Peng, John P PerdewAbstract:Unlike the local density approximation (LDA) and the Generalized Gradient approximation (GGA), calculations with meta-Generalized Gradient approximations (meta-GGA) are usually done according to the Generalized Kohn-Sham (gKS) formalism. The exchange-correlation potential of the gKS equation is non-multiplicative, which prevents systematic comparison of meta-GGA bandstructures to those of the LDA and the GGA. We implement the optimized effective potential (OEP) of the meta-GGA for periodic systems, which allows us to carry out meta-GGA calculations in the same KS manner as for the LDA and the GGA. We apply the OEP to several meta-GGAs, including the new SCAN functional [Phys. Rev. Lett. 115, 036402 (2015)]. We find that the KS gaps and KS band structures of meta-GGAs are close to those of GGAs. They are smaller than the more realistic gKS gaps of meta-GGAs, but probably close to the gaps in the exact KS band structure. The well-known grid sensitivity of meta-GGAs is much more severe in OEP calculations.
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semilocal and hybrid meta Generalized Gradient approximations based on the understanding of the kinetic energy density dependence
Journal of Chemical Physics, 2013Co-Authors: Jianwei Sun, Gustavo E. Scuseria, Bing Xiao, Robin Haunschild, Ireneusz W Bulik, John P PerdewAbstract:We present a global hybrid meta-Generalized Gradient approximation (meta-GGA) with three empirical parameters, as well as its underlying semilocal meta-GGA and a meta-GGA with only one empirical parameter. All of them are based on the new meta-GGA resulting from the understanding of kinetic-energy-density dependence [J. Sun, B. Xiao, and A. Ruzsinszky, J. Chem. Phys. 137, 051101 (2012)]10.1063/1.4742312. The obtained functionals show robust performances on the considered molecular systems for the properties of heats of formation, barrier heights, and noncovalent interactions. The pair-wise additive dispersion corrections to the functionals are also presented.
S B Trickey - One of the best experts on this subject based on the ideXlab platform.
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towards accurate orbital free simulations a Generalized Gradient approximation for the noninteracting free energy density functional
Physical Review B, 2020Co-Authors: Kai Luo, Valentin V Karasiev, S B TrickeyAbstract:For orbital-free {\it ab initio} molecular dynamics, especially on systems in extreme thermodynamic conditions, we provide the first pseudo-potential-adapted Generalized Gradient approximation (GGA) functional for the non-interacting free energy. This is achieved by systematic finite-temperature extension of our recent LKT ground state non-interacting kinetic energy GGA functional (Phys. Rev. B \textbf{98}, 041111(R) (2018)). We test the performance of the new functional first via static lattice calculations on crystalline aluminum and silicon. Then we compare deuterium equation of state results against both path-integral Monte Carlo and conventional (orbital-dependent) Kohn-Sham results. The new functional, denoted LKTF, outperforms the previous best semi-local free energy functional, VT84F (Phys.\ Rev.\ B \textbf{88}, 161108(R) (2013)), and provides modestly faster simulations. We also discuss subtleties of identification of kinetic and entropic contributions to non-interacting free-energy functionals obtained by extension from ground state orbital-free kinetic energy functionals.
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a simple Generalized Gradient approximation for the noninteracting kinetic energy density functional
Physical Review B, 2018Co-Authors: Kai Luo, Valentin V Karasiev, S B TrickeyAbstract:A simple, unconventional, nonempirical, constraint-based orbital-free Generalized Gradient approximation (GGA) noninteracting kinetic energy density functional is presented along with illustrative applications. The innovation is adaptation of constraint-based construction to the essential properties of pseudodensities from the pseudopotentials that are essential in plane-wave-basis ab initio molecular dynamics. This contrasts with constraining to the qualitatively different Kato-cusp-condition densities. The single parameter in the proposed functional is calibrated by satisfying Pauli potential positivity constraints for pseudoatom densities. In static lattice tests on simple metals and semiconductors, the LKT (for the authors' initials) functional outperforms the previous best constraint-based GGA functional, VT84F [Phys. Rev. B 88, 161108(R) (2013)], is generally superior to a recently proposed meta-GGA, is reasonably competitive with parametrized two-point functionals, and is substantially faster.
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a simple Generalized Gradient approximation for the noninteracting kinetic energy density functional
Physical Review B, 2018Co-Authors: Kai Luo, Valentin V Karasiev, S B TrickeyAbstract:A simple, novel, non-empirical, constraint-based orbital-free Generalized Gradient approximation (GGA) non-interacting kinetic energy density functional is presented along with illustrative applications. The innovation is adaptation of constraint-based construction to the essential properties of pseudo-densities from the pseudo-potentials that are essential in plane-wave-basis {\it ab initio} molecular dynamics. This contrasts with constraining to the qualitatively different Kato-cusp-condition densities. The single parameter in the new functional is calibrated by satisfying Pauli potential positivity constraints for pseudo-atom densities. In static lattice tests on simple metals and semiconductors, the new LKT functional outperforms the previous best constraint-based GGA functional, VT84F (Phys.\ Rev.\ B \textbf{88}, 161108(R) (2013)), is generally superior to a recently proposed meta-GGA, is reasonably competitive with parametrized two-point functionals, and is substantially faster.
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Generalized Gradient Approximation Exchange Energy Functional with Near-Best Semilocal Performance
2018Co-Authors: Javier Carmona-espíndola, Alberto Vela, José L. Gázquez, S B TrickeyAbstract:We develop and validate a nonempirical Generalized Gradient approximation (GGA) exchange (X) density functional that performs as well as the SCAN (strongly constrained and appropriately normed) meta-GGA on standard thermochemistry tests. Additionally, the new functional (NCAP, nearly correct asymptotic potential) yields Kohn–Sham eigenvalues that are useful approximations of the density functional theory (DFT) ionization potential theorem values by inclusion of a systematic derivative discontinuity shift of the X potential. NCAP also enables time-dependent DFT (TD-DFT) calculations of good-quality polarizabilities, hyper-polarizabilities, and one-Fermion excited states without modification (calculated or ad hoc) of the long-range behavior of the exchange potential or other patches. NCAP is constructed by reconsidering the imposition of the asymptotic correctness of the X potential (−1/r) as a constraint. Inclusion of derivative discontinuity and approximate integer self-interaction correction treatments along with first-principles determination of the effective second-order Gradient expansion coefficient yields a major advance over our earlier correct asymptotic potential functional [CAP; J. Chem. Phys. 2015, 142, 054105]. The new functional reduces a spurious bump in the CAP atomic exchange potential and moves it to distances irrelevantly far from the nucleus (outside the tail of essentially all practical basis functions). It therefore has nearly correct atomic exchange-potential behavior out to rather large finite distances r from the nucleus but eventually goes as −c/r with an estimated value for the constant c of around 0.3, so as to achieve other important properties of exact DFT exchange within the restrictions of the GGA form. We illustrate the results with the Ne atom optimized effective potentials and with standard molecular benchmark test data sets for thermochemical, structural, and response properties
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deorbitalization strategies for meta Generalized Gradient approximation exchange correlation functionals
Physical Review A, 2017Co-Authors: Daniel Mejiarodriguez, S B TrickeyAbstract:We explore the simplification of widely used meta-Generalized-Gradient approximation (mGGA) exchange-correlation functionals to the Laplacian level of refinement by use of approximate kinetic-energy density functionals (KEDFs). Such deorbitalization is motivated by the prospect of reducing computational cost while recovering a strictly Kohn-Sham local potential framework (rather than the usual Generalized Kohn-Sham treatment of mGGAs). A KEDF that has been rather successful in solid simulations proves to be inadequate for deorbitalization, but we produce other forms which, with parametrization to Kohn-Sham results (not experimental data) on a small training set, yield rather good results on standard molecular test sets when used to deorbitalize the meta-GGA made very simple, Tao-Perdew-Staroverov-Scuseria, and strongly constrained and appropriately normed functionals. We also study the difference between high-fidelity and best-performing deorbitalizations and discuss possible implications for use in ab initio molecular dynamics simulations of complicated condensed phase systems.
Dieter Cremer - One of the best experts on this subject based on the ideXlab platform.
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avoiding singularity problems associated with meta gga Generalized Gradient approximation exchange and correlation functionals containing the kinetic energy density
Journal of Chemical Physics, 2007Co-Authors: Jurgen Grafenstein, Dmitry Izotov, Dieter CremerAbstract:Convergence problems of meta-GGA (Generalized Gradient approximation) XC (exchange and correlation) functionals containing a self-interaction correction term are traced back to a singularity of the latter that occurs at critical points of the electron density. This is demonstrated for the bond critical point of equilibrium and stretched H2. A simple remedy is suggested that cures meta-XC functionals such as VSXC, TPSS, M05, M06, and their derivatives without extra cost.
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long range and short range coulomb correlation effects as simulated by hartree fock local density approximation and Generalized Gradient approximation exchange functionals
Theoretical Chemistry Accounts, 2003Co-Authors: Victor Polo, Jurgen Grafenstein, Elfi Kraka, Dieter CremerAbstract:Exchange functionals used in density functional theory (DFT) are generally considered to simulate long-range electron correlation effects. It is shown that these effects can be traced back to the self-interaction error (SIE) of approximate exchange functionals. An analysis of the SIE with the help of the exchange hole reveals that both short-range (dynamic) and long-range (nondynamic) electron correlation effects are simulated by DFT exchange where the local density approximation (LDA) accounts for stronger effects than the Generalized Gradient expansion (GGA). This is a result of the fact that the GGA exchange hole describes the exact exchange hole close to the reference electron more accurately than the LDA hole does. The LDA hole is more diffuse, thus leading to an underestimation of exchange and stronger SIE effects, where the magnitude of the SIE energy is primarily due to the contribution of the core orbitals. The GGA exchange hole is more compact, which leads to an exaggeration of exchange in the bond and the nonbonding region and negative SIE contributions. Partitioning of the SIE into intra-/interelectronic and individual orbital contributions makes it possible to test the performance of a given exchange functional in different regions of the molecule. It is shown that Hartree–Fock exchange always covers some long-range effects via interelectronic exchange while self-interaction-corrected DFT is lacking these effects.
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long range and short range coulomb correlation effects as simulated by hartree fock local density approximation and Generalized Gradient approximation exchange functionals
Theoretical Chemistry Accounts, 2003Co-Authors: Victor Polo, Jurgen Grafenstein, Elfi Kraka, Dieter CremerAbstract:Exchange functionals used in density functional theory (DFT) are generally considered to simulate long-range electron correlation effects. It is shown that these effects can be traced back to the self-interaction error (SIE) of approximate exchange functionals. An analysis of the SIE with the help of the exchange hole reveals that both short-range (dynamic) and long-range (nondynamic) electron correlation effects are simulated by DFT exchange where the local density approximation (LDA) accounts for stronger effects than the Generalized Gradient expansion (GGA). This is a result of the fact that the GGA exchange hole describes the exact exchange hole close to the reference electron more accurately than the LDA hole does. The LDA hole is more diffuse, thus leading to an underestimation of exchange and stronger SIE effects, where the magnitude of the SIE energy is primarily due to the contribution of the core orbitals. The GGA exchange hole is more compact, which leads to an exaggeration of exchange in the bond and the nonbonding region and negative SIE contributions. Partitioning of the SIE into intra-/interelectronic and individual orbital contributions makes it possible to test the performance of a given exchange functional in different regions of the molecule. It is shown that Hartree–Fock exchange always covers some long-range effects via interelectronic exchange while self-interaction-corrected DFT is lacking these effects.
Gustavo E. Scuseria - One of the best experts on this subject based on the ideXlab platform.
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semilocal and hybrid meta Generalized Gradient approximations based on the understanding of the kinetic energy density dependence
Journal of Chemical Physics, 2013Co-Authors: Jianwei Sun, Gustavo E. Scuseria, Bing Xiao, Robin Haunschild, Ireneusz W Bulik, John P PerdewAbstract:We present a global hybrid meta-Generalized Gradient approximation (meta-GGA) with three empirical parameters, as well as its underlying semilocal meta-GGA and a meta-GGA with only one empirical parameter. All of them are based on the new meta-GGA resulting from the understanding of kinetic-energy-density dependence [J. Sun, B. Xiao, and A. Ruzsinszky, J. Chem. Phys. 137, 051101 (2012)]10.1063/1.4742312. The obtained functionals show robust performances on the considered molecular systems for the properties of heats of formation, barrier heights, and noncovalent interactions. The pair-wise additive dispersion corrections to the functionals are also presented.
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Generalized Gradient approximation model exchange holes for range separated hybrids
Journal of Chemical Physics, 2008Co-Authors: Thomas M Henderson, Benjamin G Janesko, Gustavo E. ScuseriaAbstract:We propose a general model for the spherically averaged exchange hole corresponding to a Generalized Gradient approximation (GGA) exchange functional. Parameters are reported for several common GGAs. Our model is based upon that of Ernzerhof and Perdew [J. Chem. Phys. 109, 3313 (1998)]. It improves upon the former by precisely reproducing the energy of the parent GGA, and by enabling fully analytic evaluation of range-separated hybrid density functionals. Analytic results and preliminary thermochemical tests indicate that our model also improves upon the simple, local-density-based exchange hole model of Iikura et al. [J. Chem. Phys. 115, 3540 (2001)].
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restoring the density Gradient expansion for exchange in solids and surfaces
Physical Review Letters, 2008Co-Authors: John P Perdew, Gustavo E. Scuseria, Adrienn Ruzsinszky, Gabor I Csonka, Oleg A Vydrov, Lucian A Constantin, Xiaolan Zhou, Kieron BurkeAbstract:Popular modern Generalized Gradient approximations are biased toward the description of free-atom energies. Restoration of the first-principles Gradient expansion for exchange over a wide range of density Gradients eliminates this bias. We introduce a revised Perdew-Burke-Ernzerhof Generalized Gradient approximation that improves equilibrium properties of densely packed solids and their surfaces.
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meta Generalized Gradient approximation explanation of a realistic nonempirical density functional
Journal of Chemical Physics, 2004Co-Authors: John P Perdew, Jianmin Tao, Viktor N Staroverov, Gustavo E. ScuseriaAbstract:Tao, Perdew, Staroverov, and Scuseria (TPSS) have constructed a nonempirical meta-Generalized Gradient approximation (meta-GGA) [Phys. Rev. Lett. 91, 146401 (2003)] for the exchange-correlation energy, imposing exact constraints relevant to the paradigm densities of condensed matter physics and quantum chemistry. Results of their extensive tests on molecules, solids, and solid surfaces are encouraging, suggesting that this density functional achieves uniform accuracy for diverse properties and systems. In the present work, this functional is explained and details of its construction are presented. In particular, the functional is constructed to yield accurate energies under uniform coordinate scaling to the low-density or strong-interaction limit. Its nonlocality is displayed by plotting the factor Fxc that gives the enhancement relative to the local density approximation for exchange. We also discuss an apparently harmless order-of-limits problem in the meta-GGA. The performance of this functional is inv...
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climbing the density functional ladder nonempirical meta Generalized Gradient approximation designed for molecules and solids
Physical Review Letters, 2003Co-Authors: Jianmin Tao, John P Perdew, Viktor N Staroverov, Gustavo E. ScuseriaAbstract:The electron density, its Gradient, and the Kohn-Sham orbital kinetic energy density are the local ingredients of a meta-Generalized Gradient approximation (meta-GGA). We construct a meta-GGA density functional for the exchange-correlation energy that satisfies exact constraints without empirical parameters. The exchange and correlation terms respect two paradigms: one- or two-electron densities and slowly varying densities, and so describe both molecules and solids with high accuracy, as shown by extensive numerical tests. This functional completes the third rung of "Jacob's ladder" of approximations, above the local spin density and GGA rungs.
Donald G Truhlar - One of the best experts on this subject based on the ideXlab platform.
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improving rydberg excitations within time dependent density functional theory with Generalized Gradient approximations the exchange enhancement for large Gradient scheme
Journal of Chemical Theory and Computation, 2015Co-Authors: Donald G TruhlarAbstract:Time-dependent density functional theory (TDDFT) with conventional local and hybrid functionals such as the local and hybrid Generalized Gradient approximations (GGA) seriously underestimates the excitation energies of Rydberg states, which limits its usefulness for applications such as spectroscopy and photochemistry. We present here a scheme that modifies the exchange-enhancement factor to improve GGA functionals for Rydberg excitations within the TDDFT framework while retaining their accuracy for valence excitations and for the thermochemical energetics calculated by ground-state density functional theory. The scheme is applied to a popular hybrid GGA functional and tested on data sets of valence and Rydberg excitations and atomization energies, and the results are encouraging. The scheme is simple and flexible. It can be used to correct existing functionals, and it can also be used as a strategy for the development of new functionals.
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communication a global hybrid Generalized Gradient approximation to the exchange correlation functional that satisfies the second order density Gradient constraint and has broad applicability in chemistry
Journal of Chemical Physics, 2011Co-Authors: Roberto Peverati, Donald G TruhlarAbstract:We extend our recent SOGGA11 approximation to the exchange-correlation functional to include a percentage of Hartree-Fock exchange. The new functional, called SOGGA11-X, has better overall performance for a broad chemical database than any previously available global hybrid Generalized Gradient approximation, and in addition it satisfies an extra physical constraint in that it is correct to second order in the density-Gradient.
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Generalized Gradient approximation that recovers the second order density Gradient expansion with optimized across the board performance
Journal of Physical Chemistry Letters, 2011Co-Authors: Roberto Peverati, Yan Zhao, Donald G TruhlarAbstract:We present a new Generalized Gradient approximation (GGA) to the exchange-correlation functional of density functional theory, called SOGGA11, that has better overall performance for a broad chemical database than any previously available GGA and in addition is correct to second order (SO) in the density-Gradient. It provides excellent accuracy for predicting molecular bond lengths.
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construction of a Generalized Gradient approximation by restoring the density Gradient expansion and enforcing a tight lieb oxford bound
Journal of Chemical Physics, 2008Co-Authors: Yan Zhao, Donald G TruhlarAbstract:Recently, a Generalized Gradient approximation (GGA) to the density functional, called PBEsol, was optimized (one parameter) against the jellium-surface exchange-correlation energies, and this, in conjunction with changing another parameter to restore the first-principles Gradient expansion for exchange, was sufficient to yield accurate lattice constants of solids. Here, we construct a new GGA that has no empirical parameters, that satisfies one more exact constraint than PBEsol, and that performs 20% better for the lattice constants of 18 previously studied solids, although it does not improve on PBEsol for molecular atomization energies (a property that neither functional was designed for). The new GGA is exact through second order, and it is called the second-order Generalized Gradient approximation (SOGGA). The SOGGA functional also differs from other GGAs in that it enforces a tighter Lieb-Oxford bound. SOGGA and other functionals are compared to a diverse set of lattice constants, bond distances, and energetic quantities for solids and molecules (this includes the first test of the M06-L meta-GGA for solid-state properties). We find that classifying density functionals in terms of the magnitude mu of the second-order coefficient of the density Gradient expansion of the exchange functional not only correlates their behavior for predicting lattice constants of solids versus their behavior for predicting small-molecule atomization energies, as pointed out by Perdew and co-workers [Phys. Rev. Lett. 100, 134606 (2008); Perdew ibid. 80, 891 (1998)], but also correlates their behavior for cohesive energies of solids, reaction barriers heights, and nonhydrogenic bond distances in small molecules.
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databases for transition element bonding metal metal bond energies and bond lengths and their use to test hybrid hybrid meta and meta density functionals and Generalized Gradient approximations
Journal of Physical Chemistry A, 2005Co-Authors: Nathan E Schultz, Yan Zhao, Donald G TruhlarAbstract:We propose a data set of bond lengths for 8 selected transition metal dimers (Ag2, Cr2, Cu2, CuAg, Mo2, Ni2, V2, and Zr2) and another data set containing their atomization energies and the atomization energy of ZrV, and we use these for testing density functional theory. The molecules chosen for the test sets were selected on the basis of the expected reliability of the data and their ability to constitute a diverse and representative set of transition element bond types while the data sets are kept small enough to allow for efficient testing of a large number of computational methods against a very reliable subset of experimental data. In this paper we test 42 different functionals: 2 local spin density approximation (LSDA) functionals, 12 Generalized Gradient approximation (GGA) methods, 13 hybrid GGAs, 7 meta GGA methods, and 8 hybrid meta GGAs. We find that GGA density functionals are more accurate for the atomization energies of pure transition metal systems than are their meta, hybrid, or hybrid me...
