Massively parallel molecular-dynamics simulation of ice crystallisation and melting: The roles of system size, ensemble, and electrostatics

作者：English Niall J^*

来源：Journal of Chemical Physics, 2014, 141(23): 234501.

DOI：10.1063/1.4903786

Ice crystallisation and melting was studied via massively parallel molecular dynamics under periodic boundary conditions, using approximately spherical ice nano-particles (both %26quot;isolated%26quot; and as a series of heterogeneous %26quot;seeds%26quot;) of varying size, surrounded by liquid water and at a variety of temperatures. These studies were performed for a series of systems ranging in size from similar to 1 x 10(6) to 8.6 x 10(6) molecules, in order to establish system-size effects upon the nano-clusters%26quot; crystallisation and dissociation kinetics. Both %26quot;traditional%26quot; four-site and %26quot;single-site%26quot; and water models were used, with and without formal point charges, dipoles, and electrostatics, respectively. Simulations were carried out in the microcanonical and isothermal-isobaric ensembles, to assess the influence of %26quot;artificial%26quot; thermo-and baro-statting, and important disparities were observed, which declined upon using larger systems. It was found that there was a dependence upon system size for both ice growth and dissociation, in that larger systems favoured slower growth and more rapid melting, given the lower extent of %26quot;communication%26quot; of ice nano-crystallites with their periodic replicae in neighbouring boxes. Although the single-site model exhibited less variation with system size vis-a-vis the multiple-site representation with explicit electrostatics, its crystallisation-dissociation kinetics was artificially fast.

• 出版日期2014-12-21