Derivation of force theorems in density-functional theory: Application to the full-potential LMTO method

A systematic technique for deriving force theorems within density-functional theory is presented. It is based on an arbitrary guess at the response of the electrons to a shift of a nucleus, yielding a valid force theorem for each choice. Application to the full-potential linear-muffin-tin-orbital method gives a workable force expression which is unusually insensitive to deviations from self-consistency.