The crystallization of nitromethane, CH(3)NO(2), from the melt on the (100), (010), (001), and (110) crystal surfaces at 170, 180, 190, 200, 210, and 220 K has been investigated using constant-volume and -temperature (NVT) molecular dynamics simulations with a realistic, fully flexible force field [D. C. Sorescu, B. M. Rice, and D. L. Thompson, J. Phys. Chem. B 104, 8406 (2000)]. The crystallization process and the nature of the solid-liquid interface have been investigated by computing the molecular orientations, density, and radial distribution functions as functions of time and location in the simulation cell. During crystallization the translational motion of the molecules ceases first, after which molecular rotation ceases as the molecules assume proper orientations in the crystal lattice. The methyl groups are hindered rotors in the liquid; hindrance to rotation is reduced upon crystallization. The width of the solid-liquid interface varies between 6 and 13 Å (about two to five molecular layers) depending on which crystal surface is exposed to the melt and which order parameter is used to define the interface. The maximum rate of crystallization varies from 0.08 molecules ns(-1) Å(-2) for the (010) surface at 190 K to 0.41 molecules ns(-1) Å(-2) for the (001) surface at 220 K.
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Mol Divers
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School of Sciences, China Pharmaceutical University, 639 Longmian Avenue, Nanjing, 211198, People's Republic of China.
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A.V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, ul. Palchevskogo 17, Vladivostok, 690041, Russia.
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Department of Physics and Competence Centre for Catalysis, Chalmers University of Technology, SE-412 96, Göteborg, Sweden.
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State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun, P. R. China.
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