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Donald G. Truhlar - One of the best experts on this subject based on the ideXlab platform.
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localized active space pair Density Functional Theory
ChemRxiv, 2021Co-Authors: Riddhish Pandharkar, Christopher J. Cramer, Donald G. Truhlar, Matthew R Hermes, Laura GagliardiAbstract:Accurate quantum chemical methods for the prediction of spin-state energy gaps for strongly correlated systems are computationally expensive and scale poorly with the size of the system. This makes calculations for many experimentally interesting molecules impractical even with abundant computational resources. In previous work, we have shown that the localized active space (LAS) self-consistent field (SCF) method is an efficient way to obtain multi-configuration SCF wave functions of comparable quality to the corresponding complete active space (CAS) ones. To obtain quantitative results, a post-SCF method is needed to estimate the complete correlation energy. One such method is multiconfiguration pair-Density Functional Theory (PDFT), which calculates the energy based on the Density and on-top pair Density obtained from a multiconfiguration wave function. In this work we introduce localized-active-space pair-Density Functional Theory, which uses a LAS wave function for subsequent PDFT calculations. The method is tested for computing spin-state energy gaps in conjugated organic molecules and bimetallic compounds and is shown to give results within 0.05 eV of the corresponding CAS-PDFT results at a significantly lower cost.
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how well can Density Functional Theory and pair Density Functional Theory predict the correct atomic charges for dissociation and accurate dissociation energetics of ionic bonds
Physical Chemistry Chemical Physics, 2018Co-Authors: Junwei Lucas Bao, Pragya Verma, Donald G. TruhlarAbstract:The accuracy of Density Functional Theory (DFT) is often judged by predicted dissociation energies, but one should also consider charge densities as illustrated here for dissociation of heteronuclear diatomic molecules, including ionic bonds for which local Density Functionals yield erroneous results. Some hybrid Density Functionals with 100% exact exchange in Kohn–Sham DFT and the local Functionals in multiconfiguration pair-Density Functional Theory give relatively acurate dissociation energies for NaCl, and they correctly yield uncharged dissociated atoms.
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combining wave function methods with Density Functional Theory for excited states
Chemical Reviews, 2018Co-Authors: Soumen Ghosh, Christopher J. Cramer, Laura Gagliardi, Pragya Verma, Donald G. TruhlarAbstract:We review state-of-the-art electronic structure methods based both on wave function Theory (WFT) and Density Functional Theory (DFT). Strengths and limitations of both the wave function and Density Functional based approaches are discussed, and modern attempts to combine these two methods are presented. The challenges in modeling excited-state chemistry using both single-reference and multireference methods are described. Topics covered include background, combining Density Functional Theory with single-configuration wave function Theory, generalized Kohn–Sham (KS) Theory, global hybrids, range-separated hybrids, local hybrids, using KS orbitals in many-body Theory (including calculations of the self-energy and the GW approximation), Bethe–Salpeter equation, algorithms to accelerate GW calculations, combining DFT with multiconfigurational WFT, orbital-dependent correlation Functionals based on multiconfigurational WFT, building multiconfigurational wave functions from KS configurations, adding correlation...
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Self-Interaction Error in Density Functional Theory: An Appraisal
The journal of physical chemistry letters, 2018Co-Authors: Junwei Lucas Bao, Laura Gagliardi, Donald G. TruhlarAbstract:Self-interaction error (SIE) is considered to be one of the major sources of error in most approximate exchange-correlation Functionals for Kohn–Sham Density-Functional Theory (KS-DFT), and it is large with all local exchange-correlation Functionals and with some hybrid Functionals. In this work, we consider systems conventionally considered to be dominated by SIE. For these systems, we demonstrate that by using multiconfiguration pair-Density Functional Theory (MC-PDFT), the error of a translated local Density-Functional approximation is significantly reduced (by a factor of 3) when using an MCSCF Density and on-top Density, as compared to using KS-DFT with the parent Functional; the error in MC-PDFT with local on-top Functionals is even lower than the error in some popular KS-DFT hybrid Functionals. Density-Functional Theory, either in MC-PDFT form with local on-top Functionals or in KS-DFT form with some Functionals having 50% or more nonlocal exchange, has smaller errors for SIE-prone systems than doe...
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multiconfiguration pair Density Functional Theory is free from delocalization error
Journal of Physical Chemistry Letters, 2017Co-Authors: Junwei Lucas Bao, Laura Gagliardi, Y Wang, Donald G. TruhlarAbstract:Delocalization error has been singled out by Yang and co-workers as the dominant error in Kohn–Sham Density Functional Theory (KS-DFT) with conventional approximate Functionals. In this Letter, by computing the vertical first ionization energy for well separated He clusters, we show that multiconfiguration pair-Density Functional Theory (MC-PDFT) is free from delocalization error. To put MC-PDFT in perspective, we also compare it with some Kohn–Sham Density Functionals, including both traditional and modern Functionals. Whereas large delocalization errors are almost universal in KS-DFT (the only exception being the very recent corrected Functionals of Yang and co-workers), delocalization error is removed by MC-PDFT, which bodes well for its future as a step forward from KS-DFT.
Laura Gagliardi - One of the best experts on this subject based on the ideXlab platform.
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localized active space pair Density Functional Theory
ChemRxiv, 2021Co-Authors: Riddhish Pandharkar, Christopher J. Cramer, Donald G. Truhlar, Matthew R Hermes, Laura GagliardiAbstract:Accurate quantum chemical methods for the prediction of spin-state energy gaps for strongly correlated systems are computationally expensive and scale poorly with the size of the system. This makes calculations for many experimentally interesting molecules impractical even with abundant computational resources. In previous work, we have shown that the localized active space (LAS) self-consistent field (SCF) method is an efficient way to obtain multi-configuration SCF wave functions of comparable quality to the corresponding complete active space (CAS) ones. To obtain quantitative results, a post-SCF method is needed to estimate the complete correlation energy. One such method is multiconfiguration pair-Density Functional Theory (PDFT), which calculates the energy based on the Density and on-top pair Density obtained from a multiconfiguration wave function. In this work we introduce localized-active-space pair-Density Functional Theory, which uses a LAS wave function for subsequent PDFT calculations. The method is tested for computing spin-state energy gaps in conjugated organic molecules and bimetallic compounds and is shown to give results within 0.05 eV of the corresponding CAS-PDFT results at a significantly lower cost.
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combining wave function methods with Density Functional Theory for excited states
Chemical Reviews, 2018Co-Authors: Soumen Ghosh, Christopher J. Cramer, Laura Gagliardi, Pragya Verma, Donald G. TruhlarAbstract:We review state-of-the-art electronic structure methods based both on wave function Theory (WFT) and Density Functional Theory (DFT). Strengths and limitations of both the wave function and Density Functional based approaches are discussed, and modern attempts to combine these two methods are presented. The challenges in modeling excited-state chemistry using both single-reference and multireference methods are described. Topics covered include background, combining Density Functional Theory with single-configuration wave function Theory, generalized Kohn–Sham (KS) Theory, global hybrids, range-separated hybrids, local hybrids, using KS orbitals in many-body Theory (including calculations of the self-energy and the GW approximation), Bethe–Salpeter equation, algorithms to accelerate GW calculations, combining DFT with multiconfigurational WFT, orbital-dependent correlation Functionals based on multiconfigurational WFT, building multiconfigurational wave functions from KS configurations, adding correlation...
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Self-Interaction Error in Density Functional Theory: An Appraisal
The journal of physical chemistry letters, 2018Co-Authors: Junwei Lucas Bao, Laura Gagliardi, Donald G. TruhlarAbstract:Self-interaction error (SIE) is considered to be one of the major sources of error in most approximate exchange-correlation Functionals for Kohn–Sham Density-Functional Theory (KS-DFT), and it is large with all local exchange-correlation Functionals and with some hybrid Functionals. In this work, we consider systems conventionally considered to be dominated by SIE. For these systems, we demonstrate that by using multiconfiguration pair-Density Functional Theory (MC-PDFT), the error of a translated local Density-Functional approximation is significantly reduced (by a factor of 3) when using an MCSCF Density and on-top Density, as compared to using KS-DFT with the parent Functional; the error in MC-PDFT with local on-top Functionals is even lower than the error in some popular KS-DFT hybrid Functionals. Density-Functional Theory, either in MC-PDFT form with local on-top Functionals or in KS-DFT form with some Functionals having 50% or more nonlocal exchange, has smaller errors for SIE-prone systems than doe...
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multiconfiguration pair Density Functional Theory is free from delocalization error
Journal of Physical Chemistry Letters, 2017Co-Authors: Junwei Lucas Bao, Laura Gagliardi, Y Wang, Donald G. TruhlarAbstract:Delocalization error has been singled out by Yang and co-workers as the dominant error in Kohn–Sham Density Functional Theory (KS-DFT) with conventional approximate Functionals. In this Letter, by computing the vertical first ionization energy for well separated He clusters, we show that multiconfiguration pair-Density Functional Theory (MC-PDFT) is free from delocalization error. To put MC-PDFT in perspective, we also compare it with some Kohn–Sham Density Functionals, including both traditional and modern Functionals. Whereas large delocalization errors are almost universal in KS-DFT (the only exception being the very recent corrected Functionals of Yang and co-workers), delocalization error is removed by MC-PDFT, which bodes well for its future as a step forward from KS-DFT.
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multiconfiguration pair Density Functional Theory outperforms kohn sham Density Functional Theory and multireference perturbation Theory for ground state and excited state charge transfer
Journal of Chemical Theory and Computation, 2015Co-Authors: Soumen Ghosh, Donald G. Truhlar, Andrew L Sonnenberger, Chad E Hoyer, Laura GagliardiAbstract:The correct description of charge transfer in ground and excited states is very important for molecular interactions, photochemistry, electrochemistry, and charge transport, but it is very challenging for Kohn–Sham (KS) Density Functional Theory (DFT). KS-DFT exchange-correlation Functionals without nonlocal exchange fail to describe both ground- and excited-state charge transfer properly. We have recently proposed a Theory called multiconfiguration pair-Density Functional Theory (MC-PDFT), which is based on a combination of multiconfiguration wave function Theory with a new type of Density Functional called an on-top Density Functional. Here we have used MC-PDFT to study challenging ground- and excited-state charge-transfer processes by using on-top Density Functionals obtained by translating KS exchange-correlation Functionals. For ground-state charge transfer, MC-PDFT performs better than either the PBE exchange-correlation Functional or CASPT2 wave function Theory. For excited-state charge transfer, M...
Julien Toulouse - One of the best experts on this subject based on the ideXlab platform.
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Basis convergence of range-separated Density-Functional Theory
Journal of Chemical Physics, 2015Co-Authors: Odile Franck, Bastien Mussard, Eleonora Luppi, Julien ToulouseAbstract:Range-separated Density-Functional Theory is an alternative approach to Kohn-Sham Density-Functional Theory. The strategy of range-separated Density-Functional Theory consists in separating the Coulomb electron-electron interaction into long-range and short-range components, and treating the long-range part by an explicit many-body wave-function method and the short-range part by a Density-Functional approximation. Among the advantages of using many-body methods for the long-range part of the electron-electron interaction is that they are much less sensitive to the one-electron atomic basis compared to the case of the standard Coulomb interaction. Here, we provide a detailed study of the basis convergence of range-separated Density-Functional Theory. We study the convergence of the partial-wave expansion of the long-range wave function near the electron-electron coalescence. We show that the rate of convergence is exponential with respect to the maximal angular momentum L for the long-range wave function, whereas it is polynomial for the case of the Coulomb interaction. We also study the convergence of the long-range second-order Møller-Plesset correlation energy of four systems (He, Ne, N2, and H2O) with the cardinal number X of the Dunning basis sets cc-p(C)VXZ, and find that the error in the correlation energy is best fitted by an exponential in X. This leads us to propose a three-point complete-basis-set extrapolation scheme for range-separated Density-Functional Theory based on an exponential formula.
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basis convergence of range separated Density Functional Theory
Journal of Chemical Physics, 2015Co-Authors: Odile Franck, Bastien Mussard, Julien Toulouse, Eleonora LuppiAbstract:Range-separated Density-Functional Theory (DFT) is an alternative approach to Kohn-Sham Density-Functional Theory. The strategy of range-separated Density-Functional Theory consists in separating the Coulomb electron-electron interaction into long-range and short-range components and treating the long-range part by an explicit many-body wave-function method and the short-range part by a Density-Functional approximation. Among the advantages of using many-body methods for the long-range part of the electron-electron interaction is that they are much less sensitive to the one-electron atomic basis compared to the case of the standard Coulomb interaction. Here, we provide a detailed study of the basis convergence of range-separated Density-Functional Theory. We study the convergence of the partial-wave expansion of the long-range wave function near the electron-electron coalescence. We show that the rate of convergence is exponential with respect to the maximal angular momentum L for the long-range wave function, whereas it is polynomial for the case of the Coulomb interaction. We also study the convergence of the long-range second-order Moller-Plesset correlation energy of four systems (He, Ne, N2, and H2O) with cardinal number X of the Dunning basis sets cc − p(C)V XZ and find that the error in the correlation energy is best fitted by an exponential in X. This leads us to propose a three-point complete-basis-set extrapolation scheme for range-separated Density-Functional Theory based on an exponential formula.
Soumen Ghosh - One of the best experts on this subject based on the ideXlab platform.
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combining wave function methods with Density Functional Theory for excited states
Chemical Reviews, 2018Co-Authors: Soumen Ghosh, Christopher J. Cramer, Laura Gagliardi, Pragya Verma, Donald G. TruhlarAbstract:We review state-of-the-art electronic structure methods based both on wave function Theory (WFT) and Density Functional Theory (DFT). Strengths and limitations of both the wave function and Density Functional based approaches are discussed, and modern attempts to combine these two methods are presented. The challenges in modeling excited-state chemistry using both single-reference and multireference methods are described. Topics covered include background, combining Density Functional Theory with single-configuration wave function Theory, generalized Kohn–Sham (KS) Theory, global hybrids, range-separated hybrids, local hybrids, using KS orbitals in many-body Theory (including calculations of the self-energy and the GW approximation), Bethe–Salpeter equation, algorithms to accelerate GW calculations, combining DFT with multiconfigurational WFT, orbital-dependent correlation Functionals based on multiconfigurational WFT, building multiconfigurational wave functions from KS configurations, adding correlation...
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multiconfiguration pair Density Functional Theory outperforms kohn sham Density Functional Theory and multireference perturbation Theory for ground state and excited state charge transfer
Journal of Chemical Theory and Computation, 2015Co-Authors: Soumen Ghosh, Donald G. Truhlar, Andrew L Sonnenberger, Chad E Hoyer, Laura GagliardiAbstract:The correct description of charge transfer in ground and excited states is very important for molecular interactions, photochemistry, electrochemistry, and charge transport, but it is very challenging for Kohn–Sham (KS) Density Functional Theory (DFT). KS-DFT exchange-correlation Functionals without nonlocal exchange fail to describe both ground- and excited-state charge transfer properly. We have recently proposed a Theory called multiconfiguration pair-Density Functional Theory (MC-PDFT), which is based on a combination of multiconfiguration wave function Theory with a new type of Density Functional called an on-top Density Functional. Here we have used MC-PDFT to study challenging ground- and excited-state charge-transfer processes by using on-top Density Functionals obtained by translating KS exchange-correlation Functionals. For ground-state charge transfer, MC-PDFT performs better than either the PBE exchange-correlation Functional or CASPT2 wave function Theory. For excited-state charge transfer, M...
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multiconfiguration pair Density Functional Theory outperforms kohn sham Density Functional Theory and multireference perturbation Theory for ground state and excited state charge transfer
Journal of Chemical Theory and Computation, 2015Co-Authors: Soumen Ghosh, Donald G. Truhlar, Andrew L Sonnenberger, Chad E Hoyer, Laura GagliardiAbstract:The correct description of charge transfer in ground and excited states is very important for molecular interactions, photochemistry, electrochemistry, and charge transport, but it is very challenging for Kohn-Sham (KS) Density Functional Theory (DFT). KS-DFT exchange-correlation Functionals without nonlocal exchange fail to describe both ground- and excited-state charge transfer properly. We have recently proposed a Theory called multiconfiguration pair-Density Functional Theory (MC-PDFT), which is based on a combination of multiconfiguration wave function Theory with a new type of Density Functional called an on-top Density Functional. Here we have used MC-PDFT to study challenging ground- and excited-state charge-transfer processes by using on-top Density Functionals obtained by translating KS exchange-correlation Functionals. For ground-state charge transfer, MC-PDFT performs better than either the PBE exchange-correlation Functional or CASPT2 wave function Theory. For excited-state charge transfer, MC-PDFT (unlike KS-DFT) shows qualitatively correct behavior at long-range with great improvement in predicted excitation energies.
Odile Franck - One of the best experts on this subject based on the ideXlab platform.
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Basis convergence of range-separated Density-Functional Theory
Journal of Chemical Physics, 2015Co-Authors: Odile Franck, Bastien Mussard, Eleonora Luppi, Julien ToulouseAbstract:Range-separated Density-Functional Theory is an alternative approach to Kohn-Sham Density-Functional Theory. The strategy of range-separated Density-Functional Theory consists in separating the Coulomb electron-electron interaction into long-range and short-range components, and treating the long-range part by an explicit many-body wave-function method and the short-range part by a Density-Functional approximation. Among the advantages of using many-body methods for the long-range part of the electron-electron interaction is that they are much less sensitive to the one-electron atomic basis compared to the case of the standard Coulomb interaction. Here, we provide a detailed study of the basis convergence of range-separated Density-Functional Theory. We study the convergence of the partial-wave expansion of the long-range wave function near the electron-electron coalescence. We show that the rate of convergence is exponential with respect to the maximal angular momentum L for the long-range wave function, whereas it is polynomial for the case of the Coulomb interaction. We also study the convergence of the long-range second-order Møller-Plesset correlation energy of four systems (He, Ne, N2, and H2O) with the cardinal number X of the Dunning basis sets cc-p(C)VXZ, and find that the error in the correlation energy is best fitted by an exponential in X. This leads us to propose a three-point complete-basis-set extrapolation scheme for range-separated Density-Functional Theory based on an exponential formula.
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basis convergence of range separated Density Functional Theory
Journal of Chemical Physics, 2015Co-Authors: Odile Franck, Bastien Mussard, Julien Toulouse, Eleonora LuppiAbstract:Range-separated Density-Functional Theory (DFT) is an alternative approach to Kohn-Sham Density-Functional Theory. The strategy of range-separated Density-Functional Theory consists in separating the Coulomb electron-electron interaction into long-range and short-range components and treating the long-range part by an explicit many-body wave-function method and the short-range part by a Density-Functional approximation. Among the advantages of using many-body methods for the long-range part of the electron-electron interaction is that they are much less sensitive to the one-electron atomic basis compared to the case of the standard Coulomb interaction. Here, we provide a detailed study of the basis convergence of range-separated Density-Functional Theory. We study the convergence of the partial-wave expansion of the long-range wave function near the electron-electron coalescence. We show that the rate of convergence is exponential with respect to the maximal angular momentum L for the long-range wave function, whereas it is polynomial for the case of the Coulomb interaction. We also study the convergence of the long-range second-order Moller-Plesset correlation energy of four systems (He, Ne, N2, and H2O) with cardinal number X of the Dunning basis sets cc − p(C)V XZ and find that the error in the correlation energy is best fitted by an exponential in X. This leads us to propose a three-point complete-basis-set extrapolation scheme for range-separated Density-Functional Theory based on an exponential formula.