Accurate Correlation Energy Functional for Uniform Electron Gas from an Interpolation Ansatz without Fitting Parameters

We report an analytical representation of the correlation energy ec(rs, zeta) for a uniform electron gas (UEG), where rs is the Seitz radius or density parameter and zeta is the relative spin polarization. The new functional, called W20, is constructed to capture the known high-density and low-density limit (for zeta = 0 and 1) without any fitting parameters. The comparative assessment against the recent quantum Monte Carlo (QMC) results shows that the performance of the W20 functional is comparable to the popular parametrized UEG correlation functionals. On average, W20 agrees with QMC and PW92 [Phys. Rev. B 45, 13244 (1992)] within 0.01 eV, and W20 recovers the correct high- and low-density limits, whereas the QMC-data fitted UEG correlation functionals do not.