GW quasiparticle corrections to the LDA+U∕GGA+U electronic structure of bcc hydrogen

In this paper, we study the quasiparticle electronic structure of atomic hydrogen in the body-centered cubic structure for various densities. We employ the GW approach to compute the electron self energy. For this model system, we use the local density approximation (LDA)+U/generalized gradient approximation (GGA)+U method as the mean-field solution starting point, which is known to work better than LDA/GGA for systems with strongly correlated electrons. In the low-density insulating phase, we find that the calculated GW quasiparticle gap is quite insensitive to the value of the on-site repulsive U employed over a wide range of physically reasonable values. Moreover, our result for the electronic gap agrees with the measured difference between ionization energy and electron affinity in the atomic limit.