1,269 research outputs found
Stable and Efficient Linear Scaling First-Principles Molecular Dynamics for 10,000+ atoms
The recent progress of linear-scaling or O(N) methods in the density
functional theory (DFT) is remarkable. We expect that first-principles
molecular dynamics (FPMD) simulations based on DFT can now treat more realistic
and complex systems using the O(N) technique. However, very few examples of
O(N) FPMD simulations exist so far and the information for the accuracy or
reliability of the simulations is very limited. In this paper, we show that
efficient and robust O(N) FPMD simulations are now possible by the combination
of the extended Lagrangian Born-Oppenheimer molecular dynamics method, which
was recently proposed by Niklasson et al (Phys. Rev. Lett. 100, 123004 (2008)),
and the density matrix method as an O(N) technique. Using our linear-scaling
DFT code Conquest, we investigate the reliable calculation conditions for the
accurate O(N) FPMD and demonstrate that we are now able to do actual and
reliable self-consistent FPMD simulation of a very large system containing
32,768 atoms.Comment: 26 pages, 10 figures, accepted by J. Chem. Theory Compu
Time-reversible Born-Oppenheimer molecular dynamics
We present a time-reversible Born-Oppenheimer molecular dynamics scheme,
based on self-consistent Hartree-Fock or density functional theory, where both
the nuclear and the electronic degrees of freedom are propagated in time. We
show how a time-reversible adiabatic propagation of the electronic degrees of
freedom is possible despite the non-linearity and incompleteness of the
self-consistent field procedure. Time-reversal symmetry excludes a systematic
long-term energy drift for a microcanonical ensemble and the number of
self-consistency cycles can be kept low (often only 2-4 cycles per nuclear time
step) thanks to a good initial guess given by the adiabatic propagation of the
electronic degrees of freedom. The time-reversible Born-Oppenheimer molecular
dynamics scheme therefore combines a low computational cost with a physically
correct time-reversible representation of the dynamics, which preserves a
detailed balance between propagation forwards and backwards in time.Comment: 4 pages, 4 figure
Wavefunction extended Lagrangian Born-Oppenheimer molecular dynamics
Extended Lagrangian Born-Oppenheimer molecular dynamics [Niklasson, Phys.
Rev. Lett. 100 123004 (2008)] has been generalized to the propagation of the
electronic wavefunctions. The technique allows highly efficient first
principles molecular dynamics simulations using plane wave pseudopotential
electronic structure methods that are stable and energy conserving also under
incomplete and approximate self-consistency convergence. An implementation of
the method within the planewave basis set is presented and the accuracy and
efficiency is demonstrated both for semi-conductor and metallic materials.Comment: 6 pages, 3 figure
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