 
Summary: Computer Physics Communications 118 (1999) 31133
www.elsevier.nl/locate/cpc
Ab initio molecular dynamics, a simple algorithm for charge
extrapolation
Dario Alf`e 1
Geological Sciences Department, University College London, Gower Street, London WC1E 6BT, UK
Received 4 October 1998
Abstract
A new simple algorithm to extrapolate the electronic charge density in ab initio molecular dynamics runs is proposed.
The selfconsistent 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. All rights reserved.
PACS: 71.15.Pd
Keywords: Density functional calculations; Molecular dynamics
Ab initio molecular dynamics (AIMD) is a pow
erful tool to explore the properties of matter at the
microscopic level. The interaction between ions and
electrons is treated fully quantum mechanically, and
