Thermodynamic Stability of Sn4, Sn5, Sn6, and Sn7 Clusters by Knudsen Cell Mass Spectrometry

The Knudsen cell mass spectrometric method has been employed to measure the partial pressures of Sn[sub n] (n=1-7) under equilibrium conditions above liquid tin or a tin-gold alloy, contained in a graphite Knudsen cell. From the all-gas analyzed equilibria the following atomization enthalpies Δ[sub a]H[sub 0][sup °](Sn[sub n]), and enthalpies of formation, Δ[sub f]H[sub 298.15][sup °](Sn[sub n]), in kJ mol-1, have been obtained: Sn[sub 4], 750.2±14 and 450.6±14; Sn[sub 5], 990.2±22 and 512.3±22; Sn[sub 6], 1349.7±28 and 452.8±28; Sn[sub 7], 1644.2±37 and 460.0±37. The atomization energies are compared with available theoretical values