Effects of nonstoichiometry in the melting process of Y2O3 from molecular dynamics simulations

Molecular dynamics simulations in the microcanonical ensemble of liquid yttrium oxide were performed at a temperature of 3100 K. Three different Y/O ratios were used in order to find out what the role of nonstoichiometry is in the process of melting and disordering of the liquid at high temperatures. Our simulations indicate that when no oxygen vacancies are generated there is no disordering process and the crystalline structure should remain. We conclude that the melting process occurs, in the real system, when a large enough number of oxygen vacancies is generated as a result of the large thermal vibrations of superficial oxygen atoms. The apparent high coordination number for yttrium found experimentally is explained based on the overlapping of the partial radial distribution functions, which cannot be elucidated from the x-ray diffraction data but can be clearly seen from our simulations. [S0163-1829(99)08813-X].