Accelerating ab initio path integral molecular dynamics with multilevel sampling of potential surface

JOURNAL OF COMPUTATIONAL PHYSICS

卷:283

Article

Geng, Hua Y.^1,2 

[1] CAEP, Inst Fluid Phys, Natl Key Lab Shock Wave & Detonat Phys, Mianyang 621900, Sichuan, Peoples R China

[2] Cornell Univ, Baker Lab, Dept Chem & Chem Biol, Ithaca, NY 14853 USA

关键词: Path integral;    Molecular dynamics;    Ab initio method;    Quantum statistics;    Atomic hydrogen;   

DOI  :  10.1016/j.jcp.2014.12.007

来源: Elsevier

【 摘 要 】

A multilevel approach to sample the potential energy surface in a path integral formalism is proposed. The purpose is to reduce the required number of ab initio evaluations of energy and forces in ab initio path integral molecular dynamics (AI-PIMD) simulation, without compromising the overall accuracy. To validate the method, the internal energy and free energy of an Einstein crystal are calculated and compared with the analytical solutions. As a preliminary application, we assess the performance of the method in a realistic model-the FCC phase of dense atomic hydrogen, in which the calculated result shows that the acceleration rate is about 3 to 4-fold for a two-level implementation, and can be increased up to 10 times if extrapolation is used. With only 16 beads used for the ab initio potential sampling, this method gives a well converged internal energy. The residual error in pressure is just about 3 GPa, whereas it is about 20 GPa for a plain AI-PIMD calculation with the same number of beads. The vibrational free energy of the FCC phase of dense hydrogen at 300 K is also calculated with an AI-PIMD thermodynamic integration method, which gives a result of about 0.51 eV/proton at a density of r(s) = 0.912. (C) 2014 Elsevier Inc. All rights reserved.

【 授权许可】

Free