A density functional study of small AlxOy (x,y=1-4) clusters and their thermodynamic properties

Abstract

We report thermodynamic properties of small aluminium oxide clusters of mixed stoichiometric ratio AlxOy (x,y=1-4). The rigid rotator-harmonic oscillator approximation is used to calculate the partition function as it is generally applied in thermodynamic studies of polyatomic molecules. The molecular data used to set up the partition functions were computed by density functional techniques employing the BP86 gradient corrected exchange correlation functional. Thereby, the results of three species viz. AlO4, Al4O2, and Al4O3 previously not reported in the literature are included in this study. Equilibrium geometric parameters, energies, selected harmonic vibrational wave numbers of energetically low–lying stationary points are presented along with corresponding absorption coefficients. The resulting thermodynamic functions of aluminium oxides are consistent with the JANAF thermochemical data compilation. These functions are used to determine the temperature dependent chemical equilibrium partial pressure distributions for different aluminium to oxygen ratios.