Calculation of cohesive energy of Ti4O7

Abstract

The cohesive energy of Ti4O7not be determined experimentally by a Born-Haber cycle analysis because the heat of formation of this compound, one of the energies associated with steps involved in the cycle, has not been obtained experimentally. Therefore, this paper reports the calculation of the cohesive energy of Ti4O7 based on the real structure observed at 120 K by X-ray diffraction. The cohesive energy consists of the Madelung energy calculated by Ewald's method, the repulsive energy, van der Waals's energy, the zero-point energy and the energy associated with bipolarons formed in Ti4O7 at temperatures below 150 K. The calculated value for the cohesive energy is −390.26 eV per Ti4O7 “molecule”. This value is found to be nearly equal to the upper limit of the cohesive energy of the Ti4O7 “molecule” which is approximately estimated by extrapolating the experimental results for the heats of formation of TiO2 and Ti3O5 in Born-Haber cycle analyses.