MD simulation of crystal growth from CaCl2 melt

Crystal growth from supercooled CaCl2 melt has been studied by molecular dynamics (MD) simulation; the crystal has a distorted rutile type. The MD model was similar to that previously applied for NaCl. The Busing-type pair potentials the parameters of which were presented by Umesaki and Iwamoto were employed. The cases were studied that the initial interfaces between crystal and melt were the (001), (100) and (110) planes. The crystal grew only in the (001) case by MD of a nanosecond order, presumably because on every plane parallel to the (001) plane the charge neutrality is maintained. The maximum growth rate at about 100 K below the melting point was about 1 m/s, which is lower than that of NaCl-type structured crystals such as NaCl and MgO by about two orders of magnitude. The relatively slow rate may be due mainly to easy generation of the defects of this crystal which consists of ions with a ratio of one cation to two anions. The very small volume expansion on melting (0.5 %) inherent in CaCl2 seems not to play a special role on the growth rate. (C) 2003 Elsevier Science B.V. All rights reserved.