Electronic density of states, 1s core-level shifts, and core ionization energies of graphite, diamond, C3N4 phases, and graphitic C11N4

The full-potential linearized augmented plane wave method has been employed to determine electronic density of states, 1s core level shifts, and total 1s core ionization energies for the isoelectronic compounds graphite, diamond, C3N4, and graphitic C11N4. The C3N4 crystal structures studied are the graphitic, alpha, beta, cubic, and pseudocubic configurations. All the C sp(3) bonded structures have band gaps 0.5-1.5 eV smaller than that of diamond. Only the C3N4 composition of the C sp(2) phases has a band gap. The core level shifts and ionization energies are compared with x-ray photoelectron energies. The is energies of C atoms connected to zero, one, two, and three N in C11N4 are close to experimental XPS shifts and peak positions. Nearly all the N 1s energies are within the experimental nitrogen XPS energy range. The C 1s ionization energies of the tetrahedral carbon C3N4 phases are between 288.6-289.5 eV, which is 4.0-4.9 eV higher than the C 1s value of pure graphite. beta-C3N4 has the highest value. This compound has two N Is ionization energies at approximately 400.0 and 300.6 eV. [S0163-1829(99)14239-5].