Improved calculation of the electron affinity of He1s2sS3

Large-scale optimization of nonlinear parameters and tighter error-bound estimates yield an accurate value, $E_{\mathrm{nr}}=-2.178\mathrm{}0776\left(12\right)\mathrm{}$ a.u. (${}_{}{}^4{}_{}{}^{}\mathrm{He}$) for the nonrelativistic energy of ${\mathrm{He}}^{-}$ $1s2s2p{}_{}{}^4{}_{}{}^{}P_{}^o{}_{}{}^{}$, in agreement with a previous result of -2.1780740(100). Using Chung's recent calculation of relativistic and mass-polarization effects, an electron affinity $A=77.51\mathrm{}\pm 0.04$ meV is obtained. The calculation and significance of error bars in electronic structure calculations is discussed.