THE INFLUENCE OF GENERALIZED GRADIENT CORRECTIONS ON THE STRUCTURAL AND ELECTRONIC-PROPERTIES OF TELLURIUM

The structural and electronic properties of trigonal tellurium have be en investigated by the total energy-pseudopotential method within the local density approximation (LDA), without and including generalized g radient corrections (GGC). We find that the LDA causes an overbinding that is equivalent to a fictitious positive pressure, while the inclus ion of gradient corrections tends to overcorrect and have the effect o f adding a negative pressure to the system. Our results obtained withi n GGC are in good agreement with experiment showing systematic improve ment over LDA. In order to apply hydrostatic pressure we used the Clev eland-Wentzcovitch Lagrangian that optimizes the cell dimensions under compression by attributing a fictitious mass to the unit cell. It is seen that although this method is more efficient than the traditional exhaustive search of each lattice parameter, but it has some shortcomi ngs in providing accurate hydrostatic pressure in anisotropic systems. (C) 1997 Elsevier Science B.V.