1ST-PRINCIPLES STUDIES ON STRUCTURAL-PROPERTIES OF BETA-CRISTOBALITE

The structure of beta-cristobalite has been studied through a first-pr inciples total-energy minimization in the local-density approximation using a Car-Parrinello-type algorithm combined with the Vanderbilt ult rasoft pseudopotential scheme. It was found that the hypothetical orde red structure proposed by Wright and Leadbetter is favored and the res ulting structural parameters agree very well with experiment. Also, co rrelated relaxation of Si and O atoms toward alpha-cristobalite positi ons in the vicinity of domain boundaries is indicated.