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The Knudsen cell mass spectrometric method has been employed to measure the partial pressures of the Si[sub 7] and Si[sub 8] clusters under equilibrium conditions above liquid silicon, contained in a boron nitride liner inside a graphite Knudsen cell. Gaussian 2 (G2) theory and B3LYP density functional method were employed to determine the geometry, the vibrational frequencies, and the binding energy of the Si[sub 8] cluster. From the all-gas analyzed equilibria the following atomization enthalpies, Δ[sub a]H[sub 0][sup o](Si[sub n]), and enthalpies of formation, Δ[sub f]H[sub 298.15][sup o](Si[sub n]), in kJ mol-1, have been obtained: Si[sub 7], 2381±36 and 743±36; Si[sub 8], 2735±65 and 837±65. Experimental literature values for the electron affinities of Si[sub n](n=3–8) have been combined with present and previous results to obtain the bonding energies for the Si[sub n][sup -](n=3–8) cluster anions. The experimental atomization energies are compared with available theoretical values.


Copyright 2001 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.

The following article appeared in Meloni, G., Gingerich, K. A. Thermodynamic investigation of the Si[sub 7] and Si[sub 8] clusters by Knudsen cell mass spectrometry. Journal of Chemical Physics. 9/22/2001, Vol. 115 Issue 12. and may be found at



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