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, diam ond, C3N4, and graphitic C11N4. The C3N4 crystal structures studied are the graphitic, alpha, beta, cubic, and pseudocubic configurations. All the C s p(3) bonded structures have band gaps 0.5-1.5 eV smaller than that of diamo nd. Only the C3N4 composition of the C sp(2) phases has a band gap. The cor e level shifts and ionization energies are compared with x-ray photoelectro n energies. The is energies of C atoms connected to zero, one, two, and thr ee N in C11N4 are close to experimental XPS shifts and peak positions. Near ly all the N 1s energies are within the experimental nitrogen XPS energy ra nge. 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)142 39-5].