Molecular dynamics simulation of seeded crystal growth in glass

Abstract

The mechanism of non-congruent growth of a crystal from glass has been sought using molecular dynamics simulations. Specifically, as a model of this process, the growth of a lithium niobate (LiNbO₃) crystal seed sandwiched between two lithium niobosilicate (LNS) glass slabs has been simulated as a function of time and temperature. The growth of pre-existing crystal is strongly affected by the orientation of crystal seed, temperature, and the SiO₂ concentration in the surrounding LNS glass matrix. The orientation of LiNbO₃ seed surface that has inherently larger interplanar distance results in a relatively slower crystal growth. The addition of SiO₂ to LNS system significantly decreases the crystal growth, which primarily occurs in the region devoid of Si. The suppressive effect of SiO₂ on growth rate can be traced to the existence of defect complex comprising of Si substituted at the Nb site and a nearby Nb vacancy.