Nonlocal density scheme for electronic-structure calculations

Within density functional theory, a coordinate-scaling relation for the coupling-constant dependence of the exchange-correlation kernel f xc (r,rЈ;) is utilized to express the correlation energy of a many-electron system in terms of f xc . As a test of several of the available approximations for the exchange-correlation kernel, or equivalently the local-field factor, we calculate the uniform-gas correlation energy. While the random phase approximation ( f xc ϭ 0͒ makes the correlation energy per electron too negative by about 0.5 eV, the adiabatic local-density approximation ͓ f xc ϭ f xc (q ϭ 0, ϭ 0͔͒ makes a comparable error in the opposite direction. The adiabatic nonlocal approximation ͓ f xc ϭ f xc (q, ϭ 0͔͒ reduces this error to about 0.1 eV, and inclusion of the full frequency dependence ͓ f xc ϭ f xc (q,)] in an approximate parametrization reduces it further to less than 0.02 eV. We also report the wave-vector analysis and the imaginary-frequency analysis of the correlation energy for each choice of kernel.

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“…͑43͒ is chosen as in Ref. 54. Equation ͑43͒ may also be useful for the calculation of excitation energies.…”

Section: Discussionmentioning

confidence: 99%

Electron correlation energies from scaled exchange-correlation kernels: Importance of spatial versus temporal nonlocality

2000

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“…Recently, it has been shown by some of us 28,29 that an expression similar to Eq. ͑10͒ can be derived from a functional expansion of V xc , avoiding to introduce gradient expansions and their resummation.…”

Section: ͑4͒mentioning

confidence: 97%

“…29, we use the NLDA functional both to construct the pseudopotential for the element under consideration, and to calculate the geometry ͑lattice parameter͒ and the electronic structure of the solid. In the present paper, we focus on the case of silicon.…”

Section: Introductionmentioning

confidence: 99%

Exchange and correlation effects beyond the LDA on the dielectric function of silicon

et al. 1999

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The macroscopic dielectric function of crystalline silicon is calculated within density-functional theory, considering exchange and correlation effects beyond the local-density approximation. Reproposing an original idea of Hohenberg and Kohn, we consider a functional based on the exchange and correlation kernel of the homogeneous electron gas, K xc HEG . The same kernel is used in the evaluation of the dielectric matrix, keeping local-field effects into account. The results, compared with those obtained in the local-density approximation, show a limited reduction of the well-known overestimation of the macroscopic dielectric constant. Results obtained for optical and energy loss spectra are also presented.

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“…The calculations were performed within the LDA [26], PBE-GGA [22] and WC-GGA [20] functionals by fitting the total energy as a function of volume with the Birch equation of state. [27] The current APW+lo and previous pseudopotential plane wave (PPW) results [28,29,30] along with the experimental data [31,32] are presented in Tab. I.…”

Section: Bulk Structural Propertiesmentioning

confidence: 99%

Quantum size effects in Pb/Si(111) thin films from density functional calculations

Rafiee

Jalali-Asadabadi

2009

Computational Materials Science

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The Pb/Si(111) thin films were simulated within the density functional theory (DFT). The wellknown Perdew-Burke-Ernzerhof (PBE) version of the generalized gradient approximation (GGA) and its recent nonempirical successor Wu-Cohen (WC) issue were used to estimate the exchangecorrelation functional. Lattice parameters were calculated for Bulk of the Pb and Si compounds to obtain more reliable lattice mismatch at the interface to be consistent with our used full-potential method of calculations. The WC-GGA result predicts the lattice constants of the Pb and Si compounds better than the GGA when compared with experiment. We have found that the spinorbit coupling (SOC) does not significantly influence the results. Our finding is in agreement with the recent observation of the Rashba-type spin-orbit splitting of quantum well states in ultrathin Pb/Si(111) films. Our result shows, in agreement with experiment, that the top site (T1) is the most stable phase. A combination of tight σ and feeble π bonds has been found at the interface, which results in a covalent Pb-Si bond. Our calculated electric field gradient (EFG) predicts quantum size effects (QSE) with respect to the number of deposited Pb layers on the Si substrate. The QSE prediction shows that the EFG dramatically drops on going from first to second layer. The EFG calculation shows that this system is not an ideal paradigm to freestanding films.

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Nonlocal density scheme for electronic-structure calculations

Cited by 22 publications

References 35 publications

Electron correlation energies from scaled exchange-correlation kernels: Importance of spatial versus temporal nonlocality

Electron correlation energies from scaled exchange-correlation kernels: Importance of spatial versus temporal nonlocality

Exchange and correlation effects beyond the LDA on the dielectric function of silicon

Quantum size effects in Pb/Si(111) thin films from density functional calculations

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