Parameter-free calculation of single-particle electronic excitations inYH3
Physical Review B (Condensed Matter)
In recent optical experiments for YH 3 , a large band gap of almost 3 eV has been observed. In contrast, calculations within the local density approximation ͑LDA͒ result in a semimetallic band structure with a band overlap near the Fermi level of more than 1 eV. This unusually large discrepancy between the LDA results and experiment has led to suggestions that strong local correlation effects, similar to those found in transition metal oxides, are important in YH 3 . Here we conclude from
... conclude from parameter-free quasi-particle calculations within the GW approximation that YH 3 is essentially a conventional semiconductor. We argue that the experimental results can be fully understood in band structure terms without invoking strong local correlations. The unusually large error in the band structure made by LDA is traced to its poor description of the electronic structure of the hydrogen atom. Our GW results predict a fundamental band gap of only 1 eV and an optical gap of 2.6 eV, the difference being due to vanishing matrix elements for optical transitions at lower energies. Our prediction of a small fundamental gap could be experimentally confirmed by a combination of photoemission and inverse photoemission experiments.