Vitalij Lutsker - Academia.edu (original) (raw)
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![Research paper thumbnail of Erratum: “DFTB+, a software package for efficient approximate density functional theory based atomistic simulations” [J. Chem. Phys. 152, 124101 (2020)]](https://attachments.academia-assets.com/102909432/thumbnails/1.jpg)
](The Journal of Chemical Physics
The implementation of the GPU support in DFTB+, as described in Sec. III C of the original public... more The implementation of the GPU support in DFTB+, as described in Sec. III C of the original publication, 1 was developed based on a previous unpublished implementation by Jacek Jakowski. In order to acknowledge his work on this first implementation, the authors of the original publication wish to include J. Jakowski as co-author. The scientific content of the original publication is not affected.
Density functional-based tight-binding (DFTB) is a versatile, computationally efficient approxima... more Density functional-based tight-binding (DFTB) is a versatile, computationally efficient approximate electronic structure method, which is successfully applied in solid-state physics and chemistry. As an approximate Kohn-Sham density functional theory (DFT) it naturally inherits the flaws of the approximate local or gradient-corrected exchange-correlation functionals used for practical calculations. The behaviour known as delocalization problem leads to wrong description of fundamental gaps, ionization energies, response to electric fields, bond-length alternation in conjugate polymers. In this thesis we present the extension of the DFTB method to the class of range-separated hybrid exchange-correlation functionals, which significantly reduce the delocalization problem. We describe in detail the implementation and parametrization of the new scheme and apply it to a series of physical systems, where the delocalization problem of the local DFT and DFTB plays an important role.
The Journal of Chemical Physics, 2020
Note: This article is part of the JCP Special Topic on Electronic Structure Software.
The Journal of chemical physics, Jan 28, 2017
The particle-particle random phase approximation (pp-RPA) is a promising method for studying char... more The particle-particle random phase approximation (pp-RPA) is a promising method for studying charge transfer(CT) excitations. Through a detailed analysis on two-electron deficient systems, we show that the pp-RPA is always able to recover the long-distance asymptotic -1/R trend for CT excitations as a result of the concerted effect between orbital energies and the pp-RPA kernel. We also provide quantitative results for systems with relatively short donor-acceptor distances. With conventional hybrid or range-separated functionals, the pp-RPA performs much better than time-dependent density functional theory (TDDFT), although it still gives underestimated results which are not as good as TDDFT with system-dependent tuned functionals. For pp-RPA, there remain three great challenges in dealing with CT excitations. First, the delocalized frontier orbitals in strongly correlated systems often lead to difficulty with self-consistent field convergence as well as an incorrect picture with ab...
The Journal of Chemical Physics, 2015
Bridging the gap between first principles methods and empirical schemes, the density functional b... more Bridging the gap between first principles methods and empirical schemes, the density functional based tight-binding method (DFTB) has become a versatile tool in predictive atomistic simulations over the past years. One of the major restrictions of this method is the limitation to local or gradient corrected exchange-correlation functionals. This excludes the important class of hybrid or long-range corrected functionals, which are advantageous in thermochemistry, as well as in the computation of vibrational, photoelectron and optical spectra. The present work provides a detailed account of the implementation of DFTB for a long-range corrected functional in generalized Kohn-Sham theory. We apply the method to a set of organic molecules and compare ionization potentials and electron affinities with the original DFTB method and higher level theory. The new scheme cures the significant overpolarization in electric fields found for local DFTB, which parallels the functional dependence in first principles density functional theory (DFT). At the same time the computational savings with respect to full DFT calculations are not compromised as evidenced by numerical benchmark data.
Physical Review Letters, 2012
We construct a local gauge transformation to show how, in confined systems, a generic, weak nonho... more We construct a local gauge transformation to show how, in confined systems, a generic, weak nonhomogeneous SU (2) spin-orbit Hamiltonian reduces to two U (1) Hamiltonians for spinless fermions at opposite magnetic fields, to leading order in the spin-orbit strength. Using an Onsager relation, we further show how the resulting spin conductance vanishes in a two-terminal setup, and how it is turned on by either weakly breaking time-reversal symmetry or opening additional transport terminals. We numerically check our theory for mesoscopic cavities as well as Aharonov-Bohm rings.
Journal of Chemical Theory and Computation, 2013
The time-dependent density functional based tight-binding (TD-DFTB) approach is generalized to ac... more The time-dependent density functional based tight-binding (TD-DFTB) approach is generalized to account for fractional occupations. In addition, an on-site correction leads to marked qualitative and quantitative improvements over the original method. Especially, the known failure of TD-DFTB for the description of σ → π * and n → π * excitations is overcome. Benchmark calculations on a large set of organic molecules also indicate a better description of triplet states. The accuracy of the revised TD-DFTB method is found to be similar to first principles TD-DFT calculations at a highly reduced computational cost. As a side issue, we also discuss the generalization of the TD-DFTB method to spin-polarized systems. In contrast to an earlier study [Trani et al., JCTC 7 3304 (2011)], we obtain a formalism that is fully consistent with the use of local exchange-correlation functionals in the ground state DFTB method.
Journal of Chemical Theory and Computation, 2017
We present a consistent linear response formulation of the density functional based tight-binding... more We present a consistent linear response formulation of the density functional based tight-binding method for long-range corrected exchange-correlation functionals (LC-DFTB). Besides a detailed account of derivation and implementation of the method, we also test the new scheme on a variety of systems considered to be problematic for conventional local/semi-local time-dependent density functional theory (TD-DFT). To this class belong the optical properties of polyacenes and nucleobases, as well as charge transfer excited states in molecular dimers. We find that the approximate LC-DFTB method exhibits the same general trends and similar accuracy as range-separated DFT methods at significantly reduced computational cost. The scheme should be especially useful in the determination of the electronic excited states of very large molecules, for which conventional TD-DFT is supposed to fail due to a multitude of artificial low energy states.
The Journal of Chemical Physics
The implementation of the GPU support in DFTB+, as described in Sec. III C of the original public... more The implementation of the GPU support in DFTB+, as described in Sec. III C of the original publication, 1 was developed based on a previous unpublished implementation by Jacek Jakowski. In order to acknowledge his work on this first implementation, the authors of the original publication wish to include J. Jakowski as co-author. The scientific content of the original publication is not affected.
Density functional-based tight-binding (DFTB) is a versatile, computationally efficient approxima... more Density functional-based tight-binding (DFTB) is a versatile, computationally efficient approximate electronic structure method, which is successfully applied in solid-state physics and chemistry. As an approximate Kohn-Sham density functional theory (DFT) it naturally inherits the flaws of the approximate local or gradient-corrected exchange-correlation functionals used for practical calculations. The behaviour known as delocalization problem leads to wrong description of fundamental gaps, ionization energies, response to electric fields, bond-length alternation in conjugate polymers. In this thesis we present the extension of the DFTB method to the class of range-separated hybrid exchange-correlation functionals, which significantly reduce the delocalization problem. We describe in detail the implementation and parametrization of the new scheme and apply it to a series of physical systems, where the delocalization problem of the local DFT and DFTB plays an important role.
The Journal of Chemical Physics, 2020
Note: This article is part of the JCP Special Topic on Electronic Structure Software.
The Journal of chemical physics, Jan 28, 2017
The particle-particle random phase approximation (pp-RPA) is a promising method for studying char... more The particle-particle random phase approximation (pp-RPA) is a promising method for studying charge transfer(CT) excitations. Through a detailed analysis on two-electron deficient systems, we show that the pp-RPA is always able to recover the long-distance asymptotic -1/R trend for CT excitations as a result of the concerted effect between orbital energies and the pp-RPA kernel. We also provide quantitative results for systems with relatively short donor-acceptor distances. With conventional hybrid or range-separated functionals, the pp-RPA performs much better than time-dependent density functional theory (TDDFT), although it still gives underestimated results which are not as good as TDDFT with system-dependent tuned functionals. For pp-RPA, there remain three great challenges in dealing with CT excitations. First, the delocalized frontier orbitals in strongly correlated systems often lead to difficulty with self-consistent field convergence as well as an incorrect picture with ab...
The Journal of Chemical Physics, 2015
Bridging the gap between first principles methods and empirical schemes, the density functional b... more Bridging the gap between first principles methods and empirical schemes, the density functional based tight-binding method (DFTB) has become a versatile tool in predictive atomistic simulations over the past years. One of the major restrictions of this method is the limitation to local or gradient corrected exchange-correlation functionals. This excludes the important class of hybrid or long-range corrected functionals, which are advantageous in thermochemistry, as well as in the computation of vibrational, photoelectron and optical spectra. The present work provides a detailed account of the implementation of DFTB for a long-range corrected functional in generalized Kohn-Sham theory. We apply the method to a set of organic molecules and compare ionization potentials and electron affinities with the original DFTB method and higher level theory. The new scheme cures the significant overpolarization in electric fields found for local DFTB, which parallels the functional dependence in first principles density functional theory (DFT). At the same time the computational savings with respect to full DFT calculations are not compromised as evidenced by numerical benchmark data.
Physical Review Letters, 2012
We construct a local gauge transformation to show how, in confined systems, a generic, weak nonho... more We construct a local gauge transformation to show how, in confined systems, a generic, weak nonhomogeneous SU (2) spin-orbit Hamiltonian reduces to two U (1) Hamiltonians for spinless fermions at opposite magnetic fields, to leading order in the spin-orbit strength. Using an Onsager relation, we further show how the resulting spin conductance vanishes in a two-terminal setup, and how it is turned on by either weakly breaking time-reversal symmetry or opening additional transport terminals. We numerically check our theory for mesoscopic cavities as well as Aharonov-Bohm rings.
Journal of Chemical Theory and Computation, 2013
The time-dependent density functional based tight-binding (TD-DFTB) approach is generalized to ac... more The time-dependent density functional based tight-binding (TD-DFTB) approach is generalized to account for fractional occupations. In addition, an on-site correction leads to marked qualitative and quantitative improvements over the original method. Especially, the known failure of TD-DFTB for the description of σ → π * and n → π * excitations is overcome. Benchmark calculations on a large set of organic molecules also indicate a better description of triplet states. The accuracy of the revised TD-DFTB method is found to be similar to first principles TD-DFT calculations at a highly reduced computational cost. As a side issue, we also discuss the generalization of the TD-DFTB method to spin-polarized systems. In contrast to an earlier study [Trani et al., JCTC 7 3304 (2011)], we obtain a formalism that is fully consistent with the use of local exchange-correlation functionals in the ground state DFTB method.
Journal of Chemical Theory and Computation, 2017
We present a consistent linear response formulation of the density functional based tight-binding... more We present a consistent linear response formulation of the density functional based tight-binding method for long-range corrected exchange-correlation functionals (LC-DFTB). Besides a detailed account of derivation and implementation of the method, we also test the new scheme on a variety of systems considered to be problematic for conventional local/semi-local time-dependent density functional theory (TD-DFT). To this class belong the optical properties of polyacenes and nucleobases, as well as charge transfer excited states in molecular dimers. We find that the approximate LC-DFTB method exhibits the same general trends and similar accuracy as range-separated DFT methods at significantly reduced computational cost. The scheme should be especially useful in the determination of the electronic excited states of very large molecules, for which conventional TD-DFT is supposed to fail due to a multitude of artificial low energy states.