Dielectric tensor, effective charges, and phonons in α-quartz by variational density-functional perturbation theory
A new method is introduced to calculate response functions within Density Functional
Theory. It uses a conjugate-gradient algorithm applied to a variational expression from
perturbation theory. The dielectric tensor, Born effective charges, and TO and LO phonons at
q= 0 are obtained. A one-parameter scissors operator gives the dielectric tensor within 0.5%
of the experimental value. The anisotropy of the effective charge tensor is shown to be
crucial for reproducing the LO-TO splittings.
Theory. It uses a conjugate-gradient algorithm applied to a variational expression from
perturbation theory. The dielectric tensor, Born effective charges, and TO and LO phonons at
q= 0 are obtained. A one-parameter scissors operator gives the dielectric tensor within 0.5%
of the experimental value. The anisotropy of the effective charge tensor is shown to be
crucial for reproducing the LO-TO splittings.
Abstract
A new method is introduced to calculate response functions within Density Functional Theory. It uses a conjugate-gradient algorithm applied to a variational expression from perturbation theory. The dielectric tensor, Born effective charges, and TO and LO phonons at q= 0 are obtained. A one-parameter scissors operator gives the dielectric tensor within 0.5% of the experimental value. The anisotropy of the effective charge tensor is shown to be crucial for reproducing the LO-TO splittings.
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