On the free energy of disordered alloys and the moments of the density of states

ANA MARÍA LLOIS; NORAH V. COHAN

JOURNAL OF PHYSICS CONDENSED MATTER

IOP PUBLISHING LTD

Lugar: Londres; Año: 1980 vol. 13 p. 1027 - 1033

0953-8984

We calculate exact upper and lower bounds for the Helmholtz free energy of aID tight-binding disordered alloy as a function of temperature. We show that the averageof the upper and lower bounds, calculated using very few (of the order of five) exact moments of the density of states, is an excellent approximation to the free energy of the system. We also use three different approximations for the density of states of the disordered alloy and show that they all give quite similar and precise values for the free energy. Thus, if only the free energy of a disordered system is required, the average of upper and lower bounds seems to be the most convenient procedure to use. If other properties are calculated as well, then obviously some approximation to the density of states will be needed, which willcertainly be sufficient for the calculation of the free energy.