GASEOUS METAL SILICIDES .2. THERMODYNAMIC STUDY OF THE MOLECULES AUSI, AUSI2 AND AU2SI WITH A MASS-SPECTROMETER

The gaseous equilibria involving the molecules AuSi, AuSi2 and Au2Si have been studied by means of the Knudsen effusion technique combined with mass spectrometric analysis of the vapor. The experimentally determined reaction enthalpies were combined with appropriate literature data to obtain the following atomization energies (in kJ mole-1): D00[AuSi(g)] = 301.0 ± 6.0, D00[Au2Si(g)] = 582.7 ± 15 and D00[AuSi2(g)] = 602.1 ± 15. The corresponding D0298 values are: 305.2 ± 6.0, 589.1 ± 15 and 610.5 ± 15, and the standard heats of formation, ΔH0f,298, 518.6, 602.9 and 668.9, respectively. Comparison of the atomization energies of these silicon-gold molecules with the literature values for the corresponding germanium-gold and tin-gold molecules indicates similarity in the nature of bonding. © 1979.