  We present an improved field-theoretic approach to the grand-canonical
potential suitable for linear scaling molecular dynamics simulations using
forces from self-consistent electronic structure calculations. It is based on
an exact decomposition of the grand canonical potential for independent
fermions and does neither rely on the ability to localize the orbitals nor that
the Hamilton operator is well-conditioned. Hence, this scheme enables highly
accurate all-electron linear scaling calculations even for metallic systems.
The inherent energy drift of Born-Oppenheimer molecular dynamics simulations,
arising from an incomplete convergence of the self-consistent field cycle, is
circumvented by means of a properly modified Langevin equation. The predictive
power of the present linear scaling \textit{ab-initio} molecular dynamics
approach is illustrated using the example of liquid methane under extreme
conditions.
