OPTICAL-PROPERTIES STUDIED USING LINEAR-MUFFIN-TIN-ORBITAL THEORY

A new method is presented for calculating optical properties within the framework of the self-consistent linear muffin-tin orbital (LMTO) band-structure theory. We show how Green's second identity along with the commutation relation between the position and Hamiltonian operators may be used to calculate, independently of the gauge, the velocity matrix elements required for optical properties. The method has been applied to calculate the imaginary part of the dielectric function epsilon(2)(E) for FeSi and Si. Notably, the new expressions for matrix elements are also valid for Hamiltonians in which non-local potentials are included.