STRUCTURAL-PROPERTIES OF ALKALI-METALS (LI, NA AND K) IN THE GENERALIZED GRADIENT APPROXIMATION

We have studied the structural properties and the phase stability of t he alkali metals (Li, Na, and K) by using the pseudopotential density- functional total-energy calculation scheme within the recently propose d generalized-gradient approximation (GGA) of Perdew, Burke, and Ernze rhof. The present GGA calculations predict the lattice constants, the bulk moduli, and the cohesive energies of the alkali metals more accur ately than the local-density approximation calculations! but the order of the crystal energy at zero temperature is E-hcp < E-fcc < E-bcc fo r all these metals, irrespective of the exchange-correlation functiona ls used.