Nature of the insulating state

Nature of the insulating state Article

Wang, X, Chen, C. (1997). Nature of the insulating state . Physical review B (PRB), 56(12), R7049-R7052. 10.1103/PhysRevB.56.R7049

This paper reports a combined first-principles and many-body study of the nature of the insulating state in LaH(Formula presented), focusing on the role of the electron correlation, which has been suggested as the mechanism responsible for the observed insulating behavior. The first-principles local-density-approximation (LDA) calculation produces a correct lattice constant but results in a semimetallic ground state, contrary to a recent optical experiment that showed that LaH(Formula presented) is an insulator with a gap of 1.8 eV. An extended Hubbard model is constructed for LaH(Formula presented) with its parameters extracted from the results of LDA total energy calculations. An exact-diagonalization study is then carried out to study the effect of the many-body correlation. The results show that the model produces an insignificant reduction of band overlap, thus demonstrating that the insulating ground state of LaH(Formula presented) is not a Hubbard-type correlation-driven insulator. © 1997 The American Physical Society.