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 the alkali metals (Li, Na, and K) by using the pseudopotential density-functional total-energy calculation scheme within the recently proposed generalized-gradient approximation (GGA) of Perdew, Burke, and Ernzerhof. The present GGA calculations predict the lattice constants, the bulk moduli, and the cohesive energies of the alkali metals more accurately than the local-density approximation calculations, but the order of the crystal energy at zero temperature is E _hcp < E _fcc < -E _bcc for all these metals, irrespective of the exchange-correlation functionals used.