Mass spectrometric investigation of the thermodynamic properties of the Si6 molecule

Partial pressures of Si(g) and Si-6(g) over condensed silicon have been measured by Knudsen cell mass spectrometry. The atomization energy and enthalpy of formation of Si,(g) was evaluated for the reaction Si-6(g) = 6Si(g) with these partial pressures and with thermal functions derived from recent experimental and theoretical molecular parameters. The results, Delta(a)H(o)[Si-6(g)] = 1981 +/- 32 kJ mol(-1) and Delta(f)H(298.15)[Si-6(g)] = 733 +/- 41 kJ mol(-1) are compared with predictions from recent theoretical calculations.