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Electronic structure calculations using simulation cells for extended systems typically incorporate periodic boundary conditions as an attempt to mimic the real system with a practically infinite number of particles. Periodic boundary conditions introduce unphysical constraints that give rise to finite-size errors. In mean-field type calculations, the infinite size limit is achieved by simple quadrature in the Brillouin zone using a finite number of k-points. Many-body electronic structure calculations with explicit two-particle interactions cannot avail themselves of this simplification. Direct extrapolation is computationally costly while size correction with less accurate methods is frequently not sufficiently accurate. The Hartree-Fock method neglects the correlation energy, while the conventional density functional theory (DFT) uses the infinite-size limit of the exchange correlation function. Here we present a new finite-size exchange correlation function designed to be used in OFT calculations to give more accurate estimates of the finite-size errors. Applications of the method are presented, including the P2 molecule, fcc silicon, bcc sodium and BiScO3 perovskite. The method is shown to deliver rapidly convergent size-corrections. |
