Weighted Density Approximation Description of Insulating YH₃ and LaH₃

Density functional calculations within the weighted density approximation (WDA) are presented for YH$_3$ and LaH$_3$. We investigate some commonly used pair-distribution functions G. These calculations show that within a consistent density functional framework a substantial insulating gap can be obtained while at the same time retaining structural properties in accord with experimental data. Our WDA band structures agree with those of $GW$ approximation very well, but the calculated band gaps are still 1.0-2.0 eV smaller than experimental findings.