Three pillars for achieving quantum mechanical molecular dynamics simulations of huge systems: Divide-and-conquer, density-functional tight-binding, and massively parallel computation

• Published in: Journal of computational chemistry 2016-08, Vol.37 (21), p.1983-1992
• Main Authors: Nishizawa, Hiroaki, Nishimura, Yoshifumi, Kobayashi, Masato, Irle, Stephan, Nakai, Hiromi
• Format: Article
• Language: English
• Subjects: Chemical reactions; Computer simulation; density-functional tight-binding method; Geometry; Interpolation; linear-scaling divide-and-conquer method; massively parallel computation; Optimization algorithms; quantum mechanical molecular dynamics; Quantum theory
• ISSN: 0192-8651; 1096-987X
• DOI: 10.1002/jcc.24419

The linear‐scaling divide‐and‐conquer (DC) quantum chemical methodology is applied to the density‐functional tight‐binding (DFTB) theory to develop a massively parallel program that achieves on‐the‐fly molecular reaction dynamics simulations of huge systems from scratch. The functions to perform large scale geometry optimization and molecular dynamics with DC‐DFTB potential energy surface are implemented to the program called DC‐DFTB‐K. A novel interpolation‐based algorithm is developed for parallelizing the determination of the Fermi level in the DC method. The performance of the DC‐DFTB‐K program is assessed using a laboratory computer and the K computer. Numerical tests show the high efficiency of the DC‐DFTB‐K program, a single‐point energy gradient calculation of a one‐million‐atom system is completed within 60 s using 7290 nodes of the K computer. © 2016 Wiley Periodicals, Inc. The linear‐scaling divide‐and‐conquer (DC) quantum chemical methodology is applied to the density‐functional tight‐binding (DFTB) theory to develop a massively parallel program called DC‐DFTB‐K that can be routinely applied to on‐the‐fly molecular reaction dynamics simulations of large systems. Numerical tests based on calculations of water clusters in a cubic box show a single‐point energy gradient calculation of a one‐million‐atom system is completed within 60 s using 7290 nodes of the K computer.