Tests of a density-based local pseudopotential for sixteen simple metals

Abstract

A comprehensive study of the lattice dynamics, elastic moduli, and liquid metal resistivities for 16 simple metals in the bcc and fcc crystal structures is made using a density-based local pseudopotential. The phonon frequencies exhibit excellent agreement with both experiment and nonlocal pseudopotential theory. The bulk modulus is evaluated by the long wave and homogeneous deformation methods, which agree after a correction is applied to the former. Calculated bulk and Voigt shear moduli are insensitive to crystal structure, and long-wavelength soft modes are found in certain cases. Resistivity calculations confirm that electrons scatter off the whole Kohn-Sham potential, including its exchange-correlation part as well as its Hartree part. All of these results are found in second-order pseudopotential perturbation theory. However, the effect of a nonperturbative treatment on the calculated lattice constant is not negligible, showing that higher-order contributions have been subsumed into the pseudopotential by construction. For bcc sodium, the band structures of local and nonlocal pseudopotentials are found to be almost identical. ͓S0163-1829͑97͒01321-0͔

Trends in the properties and structures of the simple metals from a universal local pseudopotential

“…For use in nonperturbative calculations, the parameters should be reoptimized. 4 This reoptimization represents a possible direction for future work, as it would allow us to expand Figs. 8 and 10 to include the diamond structure, an open crystal structure for which the pseudopotential is in no sense a weak perturbation.…”

“…As a check on this method, we have reproduced the EC͑I͒ values of obtained from the phonon frequencies of Ref. 4.…”

“…While B and are essentially the same for the nearly-close-packed structures, 4,13 CЈ can vary strongly between fcc and bcc structures. Our previous work 4 with the individual pseudopotential EC͑I͒ found CЈ Ͻ0 for all the real simple metals with zу2 in the bcc structure, indicating a phonon soft-mode instability 4,5 for this structure.…”

“…Like the equilibrium r s , the properties e, B, and vary little among the fcc, hcp, and bcc structures. 4 10,18 which predicts the pressure P for any volume compression ratio V/V 0 .…”

“…1,2 In previous work, 3 we constructed local electron-ion pseudopotentials for each metal individually. In conjunction with the local-density approximation for exchange and correlation, these pseudopotentials successfully predict the bulk binding energies, bulk moduli, and phonon frequencies, 4,5 and structural energy differences for most of these metals in the face-centered-cubic ͑fcc͒, ideal hexagonal-close-packed ͑hcp͒, and body-centered-cubic ͑bcc͒ structures, as well as the liquid-metal resistivities. 4 The transferability of these pseudopotentials beyond the condensed state varies strongly from one element to another.…”