{'fraction_non_alphanumeric': 0.03581526861451461, 'fraction_numerical': 0.020735155513666354, 'mean_word_length': 5.174418604651163, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
A Rigid-Body-Based Multiple Time Scale Molecular Dynamics Simulation of Nanophase Materials

Nanophase technology achieves superior material properties by assembling nanometer-size clusters. Structures on multiple-length scales and a hierarchy of time scales are essential for the design and control of nanophase materials. However, coexistence of a wide range of length and time scales hinders atomistic simulations of these materials. A new algorithm is developed for large-scale, longtime molecular dynamics simulations by combining (1) quaternion-based, rigid-body dynamics for global cluster motions; (2) implicit integration of Newton’s equations for the coalescence of clusters; and (3) normal-mode analysis of fast atomic oscillations. The new scheme, using a time step Δt of 10-12 seconds, speeds up a conventional explicit integration scheme (Δt=2 × 10-15 seconds) by a factor of 28. A parallel implementation of the scheme achieves an efficiency of 0.94 for a 1.28-million-atom nanocrystalline silicon nitride solid on 64 nodes of an IBM SP computer.