TOTAL-ENERGY CALCULATIONS USING A GRADIENT-EXPANDED KINETIC-ENERGY FUNCTIONAL

Using an approximate kinetic-energy functional, we have performed tota l-energy calculations on hulk and surface Si. The scheme is based on t he Thomas-Fermi-von Weizsacker approximation of the kinetic-energy fun ctional. The method is applied to the ground-state configuration of c- Si and H/Si(100) surfaces. The results are compared with those of expe riments and detailed Kohn-Sham-Car-Parrinello-type calculations. Encou raging agreement is found. We also compare our results with those obta ined using the simpler Thomas-Fermi form of the kinetic-energy functio nal. In general, the von Weisacker correction improves the results.