Adaptive local basis set for Kohn–Sham density functional theory in a discontinuous Galerkin framework II: Force, vibration, and molecular dynamics calculations

Journal Article · Sat Apr 15 04:00:00 EDT 2017 · Journal of Computational Physics

DOI:https://doi.org/10.1016/J.JCP.2016.12.052· OSTI ID:22622279

Zhang, Gaigong ^[1]; Lin, Lin ^[2]; Hu, Wei ^[1]; Yang, Chao ^[1]

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1. Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)
2. Department of Mathematics, University of California, Berkeley, Berkeley, CA 94720 (United States)

Recently, we have proposed the adaptive local basis set for electronic structure calculations based on Kohn–Sham density functional theory in a pseudopotential framework. The adaptive local basis set is efficient and systematically improvable for total energy calculations. In this paper, we present the calculation of atomic forces, which can be used for a range of applications such as geometry optimization and molecular dynamics simulation. We demonstrate that, under mild assumptions, the computation of atomic forces can scale nearly linearly with the number of atoms in the system using the adaptive local basis set. We quantify the accuracy of the Hellmann–Feynman forces for a range of physical systems, benchmarked against converged planewave calculations, and find that the adaptive local basis set is efficient for both force and energy calculations, requiring at most a few tens of basis functions per atom to attain accuracies required in practice. Since the adaptive local basis set has implicit dependence on atomic positions, Pulay forces are in general nonzero. However, we find that the Pulay force is numerically small and systematically decreasing with increasing basis completeness, so that the Hellmann–Feynman force is sufficient for basis sizes of a few tens of basis functions per atom. We verify the accuracy of the computed forces in static calculations of quasi-1D and 3D disordered Si systems, vibration calculation of a quasi-1D Si system, and molecular dynamics calculations of H{sub 2} and liquid Al–Si alloy systems, where we show systematic convergence to benchmark planewave results and results from the literature.

• OSTI ID: 22622279
• Journal Information: Journal of Computational Physics, Journal Name: Journal of Computational Physics Vol. 335; ISSN JCTPAH; ISSN 0021-9991
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ACCURACY
ALLOY SYSTEMS
ATOMS
BENCHMARKS
COMPUTERIZED SIMULATION
CONVERGENCE
DENSITY FUNCTIONAL METHOD
ELECTRONIC STRUCTURE
HYDROGEN
LIQUIDS
MOLECULAR DYNAMICS METHOD
OPTIMIZATION
SILICON ALLOYS