Electronic density of states,1score-level shifts, and core ionization energies of graphite, diamond,C3N4phases, and graphiticC11N4

Abstract

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, ${\mathrm{C}}_{3}{\mathrm{N}}_{4},$ and graphitic ${\mathrm{C}}_{11}{\mathrm{N}}_{4}.$ The ${\mathrm{C}}_{3}{\mathrm{N}}_{4}$ crystal structures studied are the graphitic, $\ensuremath{\alpha},$ $\ensuremath{\beta},$ cubic, and pseudocubic configurations. All the $\mathrm{C} {\mathrm{sp}}^{3}$ bonded structures have band gaps 0.5--1.5 eV smaller than that of diamond. Only the ${\mathrm{C}}_{3}{\mathrm{N}}_{4}$ composition of the $\mathrm{C} {\mathrm{sp}}^{2}$ phases has a band gap. The core level shifts and ionization energies are compared with x-ray photoelectron energies. The $1s$ energies of C atoms connected to zero, one, two, and three N in ${\mathrm{C}}_{11}{\mathrm{N}}_{4}$ are close to experimental XPS shifts and peak positions. Nearly all the $\mathrm{N} 1s$ energies are within the experimental nitrogen XPS energy range. The $\mathrm{C} 1s$ ionization energies of the tetrahedral carbon ${\mathrm{C}}_{3}{\mathrm{N}}_{4}$ phases are between 288.6--289.5 eV, which is 4.0--4.9 eV higher than the $\mathrm{C} 1s$ value of pure graphite. $\ensuremath{\beta}\ensuremath{-}{\mathrm{C}}_{3}{\mathrm{N}}_{4}$ has the highest value. This compound has two $\mathrm{N} 1s$ ionization energies at approximately 400.0 and 400.6 eV.