Mass Spectrometric Study of Inter-Group IVB Molecules

Abstract

The systems germanium-graphite and germanium-silicon-carbon have been studied. Several gaseous molecules containing Ge, Si, and/or C were observed and their dissociation energies determined from measured partial pressures. A general picture of the dissociation energies of di-, tri-, and tetraatomic intergroup IVB molecules is deduced from these measurements. Incidental to this study the vapor pressure of pure Si was determined; the result confirms the heat of sublimation obtained previously.

Molar atomization enthalpies and molar enthalpies of formation of GeSi, GeSi2, Ge2Si, and Ge2Si2by Knudsen-effusion mass spectrometry

“…for GeSi(g), and 662.6 kJ·mol −1 and 672.2 kJ·mol −1 for Ge 2 Si(g). These values, although slightly less than Drowart et al (7) deduced, are very close to those obtained in the present study. Since our results for GeSi(g) and Ge 2 Si(g) represent mean values of a larger number of measurements, they may be considered as more reliable.…”

“…Uncertainties in the F°ms were assumed to be 2 J·K −1 ·mol −1 for GeSi(g), 4 J·K −1 ·mol −1 for GeSi 2 (g) as well as Ge 2 Si(g), and 6 J·K −1 ·mol −1 for Ge 2 Si 2 . Our selected value for the standard molar atomization enthalpy of GeSi(g) is consistent with that: (297221) kJ·mol −1 , reported by Drowart et al (7) The theoretical prediction of the standard molar dissociation enthalpy D°m by Andzelm et al (9) is 365.7 kJ·mol −1 for the ground state. This value is much higher than that obtained by the thermochemical method even after taking into account the zero-temperature energy which is 12.3 kJ·mol −1 corresponding to the vibrational wavenumber chosen by us.…”

“…Our selected value is about 20 kJ·mol −1 less than this, but still in agreement within the error limits. To make the comparison of our results with those of Drowart et al (7) more meaningful, we traced back I(i + )/I(Ge + ) for i=Ge, Ge 2 , Si, GeSi, and Ge 2 Si, from the partial pressures reported by these authors, and treated them in the same way as the intensities obtained in the present study. Lack of information forced us to use the intensity ratios at a single electron energy of 2.1 aJ, but the ratio for any ion was within only three per cent of that calculated at 1.9 aJ or 2.4 aJ.…”

“…A value of (686230) kJ·mol −1 may be deduced from the results of Drowart et al (7) for the standard molar atomization enthalpy of Ge 2 Si(g). Our selected value is about 20 kJ·mol −1 less than this, but still in agreement within the error limits.…”

“…The only equilibrium mass-spectrometric investigation reported on (germanium + silicon) gaseous species is by Drowart et al (7) The recent mass-spectrometric study by Bergman et al (8) pertains to thermodynamics of the condensed phase. In a theoretical study, Andzelm et al (9) calculated standard molar enthalpy of dissociation D°m values for the predicted ground state 3 S − and the low-lying excited states 3 P and 1 S + * of GeSi.…”