Thermodynamic investigation of small homonuclear and heteronuclear molecules containing silicon and germanium

Abstract

The equilibrium involving gaseous species above the condensed systems Y/Ge, Y/Si, Sc/Ge, Sc/Si, Pd/Ge and Ni/Ge have been experimentally investigated at elevated temperatures by means of the high temperature mass spectrometric technique. The previously known molecules Ge(,2), Ge(,3), Ge(,4), and Ge(,5) have been more thoroughly investigated, by employing the reaction Ge(,n) = nGe. The atomization energies, (DELTA)H(,(alpha),0)('0) calculated were 253.5 (+OR-) 8.9 kJ mol('-1) for Ge(,2), 600.7 (+OR-) 15.8 kJ mol('-1) for Ge(,3) (cyclic), 1018 (+OR-) 22 kJ mol('-1) for Ge(,4) (tetrahedral) and 1381 (+OR-) 30 kJ mol('-1) for Ge(,5) (trigonal bipyramid). The previously unknown molecules YGe, YSi, YSi(,2), ScGe, ScSi, PdGe(,2), PdGe(,3) and NiGe(,2) have been shown to exist in the vapor phase above the respective liquid solutions. Also, reported and observed were the previously reported molecules Si(,2), AuGe, AgGe, PdGe and NiGe. Second- and third-law enthalpy changes were determined from the experimental data for the following gaseous reactions: Si(,2) = 2Si, YGe = Y + Ge, AuGe = Au + Ge, PdGe = Pd + Ge, NiGe = Ni + Ge and MGe(,n) + (n-1)M = nMGe (where M = Ni, Pd and n = 2 or 3). In addition, third-law enthalpy changes were evaluated for the following gaseous reactions: YSi = Y Si, YSi(,2) = Y + 2Si, ScGe = Sc + Ge, AuGe + Sc = ScGe + Au, ScSi = Sc + Si, AgGe = Ag + Ge and AgGe + Ag = Ge + Ag2. The values of these reaction enthalpies have been combined with necessary ancillary literature values to give the dissociation energies, D(,0)('0), of the diatomic molecules; and the atomization energies, (DELTA)H(,(alpha),0)('0), of the various polyatomic molecules assuming different molecular structures....