Alternative form of the linear-response contribution to the exchange-correlation energy functional

The linear-response contribution to the exchange-correlation energy functional Exc[n] of density-functional theory is reconsidered. An alternative form for this functional is suggested that resolves the convergence problems for finite systems inherent in the original form introduced by Hohenberg and Kohn [Phys. Rev. 136B, 864 (1964)]. Within the exchange-only approximation in which the linear response kernel is known exactly and the optimized-potential model serves as a rigorous comparative standard, the present functional is applied to spherical atoms and jellium spheres. Self-consistent results for these systems indicate that this functional might be worth a more detailed examination.