Local-density-approximation study of LaS and SmS

Abstract
Structural properties of LaS and SmS have been calculated within the local-density approximation (LDA) with use of a highly accurate general-potential linearized augmented-plane-wave method. The calculated lattice parameter of SmS is 7.6% smaller than the experimental value and, moreover, the calculations do not show any indication of the experimentally observed isostructural phase transition. Parallel calculations in which f-electron hybridization was suppressed yielded a lattice parameter and bulk modulus in good agreement with the observed values. Based on this and the good agreement obtained with experiment for the chemically similar compound LaS, we conclude that the LDA does not adequately describe the localization of the f electrons in SmS and that this failure of the LDA precludes its use in an adequate description of the structural properties of this material.

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