Fellows, it is me again.
I am continuing my work on the dissertation, and have received a new challenge from my mentor (we had solved some of the others) regarding the work in it. He seems to be concerned about the unoccupied eigenstates I plotted for some of the materials I am using in the dissertation. For the examples I am posting on this topic, I am using monolayer hexagonal boron nitride, whose calculations I performed with a 40x40x20 LDA-PZ grid and DZDP (double zeta double polarized). I obtained the eigenstates near the Fermi energy level at Gamma, K, and M. As h-BN is isoelectronic with graphene, both have the same number of eigenstates. In the case of monolayer h-BN, the occupied eigenstates end with eigenstate #3 (starting from #0), and the unoccupied energies begin with eigenstate #4. These eigenstates are the solid-state equivalents of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), and are used primarily to help my chemistry-oriented committee understand my work.
When I plotted the LUMO eigenstate at Gamma for h-BN, I obtained an orbital that looks quite different. It is quite easy to figure out which orbitals contribute to the eigenstates that are occupied, but virtual orbitals are challenging in terms of physical meaning. In h-BN, I do get N-centered orbitals for the occupied eigenstates, as they are electron-rich. The boron atoms are primarily used for the empty orbitals (unoccupied energy levels), as they are electron-poor.
Can you find out what orbitals contribute to the Gamma LUMO in h-BN? I sometimes get the same thing in orbital images using bilayer structures with h-BN in them. Do you have anything else to tell me about unoccupied orbitals near the Fermi energy level? They generally arise from mixing of atomic or group orbitals (very useful for molecular orbitals).
