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Knudsen effusion mass spectrometric studies are conducted to find the equilibrium partial pressures of C2-C7 over graphite and are combined with thermal functions for linear C4-C7. Gaseous C4 and C5 give new thermal functions and the thermal functions of C2-C5 are used in the calculation of enthalpies of formation. The enthalpies of formation of C4 and C5 are in good agreement with theoretical expectations.

Studies the electronic states and nature of bonding in the molecule MoC by all electron ab initio calculations. Basis sets and Hartree-Fock calculations on MoC; Results of multiconfiguration self-consistent field calculations; Dissociation energy of MoC.

Calculates the thermal functions of silicon nitride from theoretical molecular constants. Partial pressures after condensed phase mixtures were evaporated from boron nitride Knudsen cells; Ethalpy change of the dissociation reaction; Comparison of experimental and theoretical bond dissociation.

The equilibria involving the gaseous species above the Y–Ge and Y–Si alloy systems have been experimentally investigated by the high temperature mass spectrometer technique. The gaseous molecules YGe, YSi, and YSi2 were identified and their partial pressures were measured as a function of temperature. The experimentally determined reaction enthalpies were combined with appropriate literature data to obtain the following atomization energies, ΔH○a,0 and standard heats of formation, ΔH○f,298 , in kJ mol-1: YGe, 275.4 ± 11.4 and 522.4 ± 11.4; YSi, 253.8 ± 17.3 and 625.3 ± 17.3; YSi2, 800 ± 21 and 528 ± 21. [ABSTRACT FROM AUTHOR]

In the present work we present results of all electron ab initio multiconfiguration self-consistent-field calculations of eight electronic states of the molecule YC. Also reported are the calculated spectroscopic constants. The predicted electronic ground state is 4Π, but this state is found to be separated from a 2Π state by only 225 cm-1, and by 1393 cm-1 from a 2Σ+ state. The chemical bond in the 4Π ground state is mainly due to the formation of a bonding molecular orbital composed of the 4dπ of Y and the 2pπ on C. The 5s electrons of Y are partly transferred to the 2pσ orbital on C, and they hardly contribute to the bonding. The chemical bond in the YC molecule is polar with charge transfer from Y to C giving rise to a dipole moment of 3.90 D at 3.9 a.u. in the 4Π ground state. Mass spectrometric equilibrium investigations in the temperature range 2365–2792 K have resulted in the dissociation energy D0°=414.2±14 kJ mol-1 for YC(g), and a standard heat of formation ΔHf,298.15°=708.1±16 kJ mol-1. [ABSTRACT FROM AUTHOR]

All electron ab initio Hartree–Fock (HF) and configuration interaction (CI) calculations have been applied to investigate the low-lying electronic states of the NiGe molecule. The ground state of the NiGe molecule is predicted to be 1Σ+. The chemical bond in the 1Σ+ ground state is a double bond composed of one σ and one π bond. The σ bond is due to a delocalized molecular orbital formed by combining the Ni 4s and the Ge 4pσ orbitals. The π bond is a partly delocalized valence bond, originating from the coupling of the 3dπ hole on Ni with the 4pπ electron on Ge. The low-lying electronic states of the NiGe molecule have all been characterized by the symmetry of the hole in the 3d shell of Ni. The dissociation energy of the NiGe molecule has been determined from our high temperature mass spectrometric equilibrium data in combination with the theoretical results as D○0 =286.8±10.9 kJ mol-1. The standard heat of formation of the NiGe molecule has been obtained as ΔH○f,298 =514±12 kJ mol-1. [ABSTRACT FROM AUTHOR]

In the present work we present all-electron ab initio Hartree–Fock (HF) and configuration interaction (CI) calculations of six electronic states of the PdGe molecule. The molecule is predicted to have a 3Π ground state and two low-lying excited states 3Σ- and 1Σ+. The electronic structure of the PdGe molecule has been rationalized in a simple molecular orbital picture. As part of the PdGe molecule the Pd atom essentially retains its (4d)10 ground term configuration. The chemical bond in the PdGe molecule has been interpreted in terms of donation and backdonation of charge. The bond is polar with a small charge transfer from the Pd to the Ge atom. The dissociation energy of the PdGe molecule has been determined from the mass spectrometric equilibrium data combined with the theoretical results as D00 =252.0±10.5 kJ mol-1. [ABSTRACT FROM AUTHOR]

Investigates the thermodynamic properties of small germanium-tin clusters. Application of the Knudsen effusion mass spectrometric method; Use of the rigid-rotor harmonic-oscillator approximation on thermal function evaluation; Bond lengths and angles selected for germanium-tin clusters.