Density functional theory based on the generalized gradient approximation to the exchange and correlation energy is shown to correct a qualitative error of the local density approximation in describing a high-pressure phase transition of ${\mathrm{SiO}}_2$. Advantages of an adaptive curvilinear coordinate method for such generalized gradient calculations are discussed.

• Received 16 October 1995

DOI:https://doi.org/10.1103/PhysRevLett.76.660