Effects of an external electromagnetic field on rutile Tio2: A molecular dynamics study

Non-equilibrium molecular dynamics simulations of the bulk rutile phase of TiO₂ have been carried out in an intense external electromagnetic field with frequency in the microwave to far-infrared range. Simulations were performed in constant-volume ensembles with and without a thermostat coupled to the atomic degrees of freedom, at 298 K and from 298 K to well above the crystal melting temperature, respectively. Fields were applied along the a and c crystallographic directions. Both the Lekner and Ewald techniques were used to handle long-range electrostatics and the impact of different choices of Ewald parameters on the results has been evaluated. It was found that the ions respond rapidly to the field. The peaks and troughs in the Ti-Ti radial distribution functions were sharpened relative to the zero-field case at the instants of maximum electric field intensity, but little evidence of this was found for the Ti-O or O-O distributions. For pure Newtonian dynamics, the 500 GHz field excited the vibrational modes to the greatest extent, raising the system temperature at the fastest rate. For temperatures above 2000-2500 K, the crystal structure was found to melt. In the canonical ensemble, the 50 GHz field led to the greatest enhancement of ionic translational mobility.