Theoretical study of the cohesive and structural properties of Mo and W in bcc, fcc, and hcp structures

The structural properties of Mo and W in the bcc, fcc, and hcp structures are calculated using a fully-self-consistent pseudopotential linear combination of atomic orbitals method. Equilibrium lattice constants, cohesive energies, bulk moduli, differences in structural energies, and Mulliken-population analyses are obtained. For both elements, the bcc structure is found to be the most stable while the fcc and hcp structures have very similar cohesive energies. We find that the difference in the sum of eigenvalues gives the correct sign but not the magnitude for the difference in total energy between the bcc and fcc structures.