Cohesive energy and theP Vrelation for fcc neon in two variants of theXαmodel

The cohesive energy and associated $\mathrm{PV}$ relation for fcc neon have been calculated in the muffin-tin approximation via the augmented-plane-wave statistical-exchange ($\mathrm{A}\mathrm{P}\mathrm{W}-X\alpha$) method. Exchange parameters of 0.72997 (Schwarz's ${\alpha }_{\mathrm{VT}}$), 0.66667 (the Kohn-Sham-Gaspar value) and 0.500 were used. In all cases, the static lattice is significantly overbound, the amount of overbinding lessening with decreasing $\alpha$. The introduction of a simple radial independence ($\alpha =0.7772\mathrm{}$ for $r<\mathrm{}{r}_c$, $\alpha =\frac{2}{3}$ for $r>\mathrm{}{r}_c$ with $r_c$ some suitable change point inside the APW sphere) into the model does not cure the overbinding.