Ab initio molecular dynamics, a simple algorithm for charge extrapolation

A new simple algorithm to extrapolate the electronic charge density in ab initio molecular dynamics runs is proposed. The self-consistent charge density is decomposed in two parts, the first part is the sum of the atomic charge densities, and the second is its difference with the latter. The charge at time t + dt is constructed using the sum of the atomic charges and a second order extrapolation on the charge difference. The scheme is tested on a 64 atom liquid iron simulation under Earth's core conditions. A comparison with a simple second order extrapolation of the whole charge density shows that the new algorithm is significantly faster. (C) 1999 Elsevier Science B.V.