CALCULATION OF TOTAL ENERGIES IN MULTICOMPONENT OXIDES

The accuracy of different total-energy methods to compute the properti es of multicomponent oxides is studied. These materials have typically large unit cells and consequently, computer-running time consideratio ns become, important. We show that while highly sophisticated quantum- mechanics techniques such as pseudopotentials or the full-potential li nearized-augmented-plane-wave method can be used to accurately compute materials properties, they may require prohibitively long computer ru ns in oxides, On the other hand, simple potential models, or even fast quantum-mechanics methods such as the spherical self-consistent atomi c deformation or the linear muffin-tin orbital method (in the atomic s phere approximation), are not always reliable to study oxides, Charge transfer, breathing of the oxygen ions, and nonspherical charge relaxa tions are some of the factors that can make any of these schemes fail. However, it is not necessary to always use sophisticated techniques. Ne show that the self-consistent tight-binding formalism can be used a s an interpolation tool to extend the results of accurate calculations for a few compounds in a system to the rest of them. This opens new p ossibilities for the use of ab initio methods to study technologically -relevant materials properties, such as the temperature behavior of ox ides, since formation energies of many different compounds al 0 K art: a crucial input to these models.