Recent developments in libxc — A comprehensive library of functionals for density functional theory

Lehtola, Susi; Steigemann, Conrad; Oliveira, Micael J. T.; Marques, Miguel A. L.

doi:10.1016/j.softx.2017.11.002

Cited by 579 publications

(470 citation statements)

References 44 publications

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“…Goedecker-Teter-Hutter pseudopotentials (GTH) of LDA (Pade) form are used for approximating the potential due to the usage of the LDA form of the xc-functional as the reference functional to compare with the parametrized LDA form incorporating finite temperatures, hereafter referred to as GDSMFB [73,196]. The GDSMFB functional is accessed in the CP2K code using the library of exchange-correlation functionals (LIBXC) commonly supported by DFT codes [197,198].…”

Section: B Equation Of State Of Warm Dense Hydrogenmentioning

confidence: 99%

Ab initio simulation of warm dense matter

et al. 2020

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Warm dense matter (WDM) -an exotic state of highly compressed matter -has attracted high interest in recent years in astrophysics and for dense laboratory systems. At the same time, this state is extremely difficult to treat theoretically. This is due to the simultaneous appearance of quantum degeneracy, Coulomb correlations and thermal effects, as well as the overlap of plasma and condensed phases. Recent breakthroughs are due to the successful application of density functional theory (DFT) methods which, however, often lack the necessary accuracy and predictive capability for WDM applications. The situation has changed with the availability of the first ab initio data for the exchange-correlation free energy of the warm dense uniform electron gas (UEG) that were obtained by quantum Monte Carlo (QMC) simulations, for recent reviews, see Dornheim et al., Phys. Plasmas 24, 056303 (2017) and Phys. Rep. 744, 1-86 (2018). In the present article we review recent further progress in QMC simulations of the warm dense UEG: namely, ab initio results for the static local field correction G(q) and for the dynamic structure factor S(q, ω). These data are of key relevance for the comparison with x-ray scattering experiments at free electron laser facilities and for the improvement of theoretical models.In the second part of this paper we discuss simulations of WDM out of equilibrium. The theoretical approaches include Born-Oppenheimer molecular dynamics, quantum kinetic theory, timedependent DFT and hydrodynamics. Here we analyze strengths and limitations of these methods and argue that progress in WDM simulations will require a suitable combination of all methods. A particular role might be played by quantum hydrodynamics, and we concentrate on problems, recent progress, and possible improvements of this method.

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Section: B Equation Of State Of Warm Dense Hydrogenmentioning

confidence: 99%

Ab initio simulation of warm dense matter

et al. 2020

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“…In the present work, we describe the extension of the atomic program in HelFEM to the description of atoms with spherical symmetric density via fractional occupation numbers. Alike the other programs in HelFEM, the spherically symmetric atomic program is interfaced to the libxc library of density functionals [92] and can be used with all supported density functionals therein. Specialized implementations for atomic calculations with fractional occupations are developed for local density (LDA) and generalized gradient (GGA) functionals as well as HF exchange, yielding significant reductions in the dimensionality of the problem, whereas meta-GGA functionals can be used via an interface to the algorithms previously developed in ref.…”

Section: Introductionmentioning

confidence: 99%

Fully numerical calculations on atoms with fractional occupations and range-separated exchange functionals

Lehtola

2020

Phys. Rev. A

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A recently developed finite element approach for fully numerical atomic structure calculations [S. Lehtola, Int. J. Quantum Chem. 119, e25945 (2019)] is extended to the description of atoms with spherically symmetric densities via fractionally occupied orbitals. Specialized versions of Hartree-Fock as well as local density and generalized gradient approximation density functionals are developed, allowing extremely rapid calculations at the basis set limit on the ground and low-lying excited states even for heavy atoms.The implementation of range-separation based on the Yukawa or complementary error function (erfc) kernels is also described, allowing complete basis set benchmarks of modern range-separated hybrid functionals with either integer or fractional occupation numbers. Finally, computation of atomic effective potentials at the local density or generalized gradient approximation levels for the superposition of atomic potentials (SAP) approach [S. Lehtola, J. Chem. Theory Comput. 15, 1593] that has been shown to be a simple and efficient way to initialize electronic structure calculations is described.The present numerical approach is shown to afford beyond microhartree accuracy with a small number of numerical basis functions, and to reproduce literature results for the ground states of atoms and their cations for 1 ≤ Z ≤ 86. Our results indicate that the literature values deviate by up to 10 µE h from the complete basis set limit. The numerical scheme for the erfc kernel is shown to work by comparison to results from large Gaussian basis set calculations from the literature. Spin-restricted ground states are reported for Hartree-Fock and Hartree-Fock-Slater calculations with fractional occupations for 1 ≤ Z ≤ 118.

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“…All DFT and TDDFT calculations were performed with the Amsterdam Density Functional (ADF) software package in versions 2013 and 2018, using the libxc library for range‐separated hybrid functionals. For the TDDFT calculations, the PBE functional, the B3LYP global hybrid xc functional, and the ω B97X range‐separated hybrid functional were used.…”

Section: Computational Methodsologymentioning

confidence: 99%

Van der Waals effects on structure and optical properties in organic photovoltaics

Götz

Rodríguez

Castillo-Alvarado

et al. 2019

Int J of Quantum Chemistry

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We have recently reported that dispersion forces can have drastic effects on the structure and charge separation in organic photovoltaics (OPVs) (Martinez et al., J. Phys. Chem. C 121, 20 134 [2017]). Here we investigate dimer complexes formed by the polymer P3HT and the fullerene derivative PCBM. We show how van der Waals (vdW) interactions affect the geometrical structure, which has strong effects on the electronic structure and UV‐Vis absorption spectrum. Time‐dependent density functional theory calculations demonstrate that the experimentally observed blue‐shift of the absorption maximum of P3HT/PCBM OPV cells with respect to pure P3HT results mainly from distortions in P3HT due to vdW interactions between donor and acceptor fragments. Reduced absorption in the red region of the UV‐Vis spectrum results from distortions of P3HT and small charge transfer between P3HT and PCBM. These results are in qualitative agreement with experiments and recent theoretical results on the corresponding solid‐state films.

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Recent developments in libxc — A comprehensive library of functionals for density functional theory

Cited by 579 publications

References 44 publications

Ab initio simulation of warm dense matter

Ab initio simulation of warm dense matter

Fully numerical calculations on atoms with fractional occupations and range-separated exchange functionals

Van der Waals effects on structure and optical properties in organic photovoltaics

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