The many-body expansion of the potential energy function for elemental clusters

The many-body expansion of the potential energy function of elemental clusters is examined in general terms in regard to its convergence for microclusters and the bulk phase. The systems Be_n and Li_n are examined in detail. For Li it is clear that the many-body expansion has no low-order convergence, but it is shown that a potential of the form gives good binding energies for Li_n (3<n?9) and also a good value for the heat of atomization of the bcc crystal.     

Sum-over-states calculation of the nuclear spin coupling constant of hydrogen fluoride

The calculations of the spin-spin coupling constant of HF using extended-basis SCF orbitals which were made originally by Kato and Saika have been re-investigated. The calculated coupling constant is still found to be positive (836 hz) if the approximations introduced by Kato and Saika for the excited state energies are removed. Configuration interaction amongst the excited states does not significantly improve the convergence of the sum-over-state expression for J. It is shown that there should be an isotope effect on the reduced coupling constant which is largely determined by the anharmonic terms of the potential.     

The calculation of fluorine hyperfine interactions in π-electron radicals

Q factors have been calculated for fluorine hyperfine interaction in π-electron radicals using an independent-electron model for the σ orbitals. It is shown that the off-diagonal elements give an important contribution to fluorine coupling constants. Combining these Q factors with calculated π-electron spin densities of fluoro-nitrobenzenes gives good agreement with experimental coupling constants.     

The photoelectron spectra of the halomethanes

The photoelectron bands associated with ionization from the formally non-bonding p orbitals of the halogen atoms in the halomethanes have been interpreted in terms of a pseudo one-electron hamiltonian. Account has been taken of interactions between the halogen atoms, of interactions between the halogen p orbitals and the σ-bonding orbitals, and of spin-orbit coupling. This model leads to a systematic assignment of all the bands of the chloro and bromomethanes, and gives a satisfactory account of the spin-orbit splittings in the bromomethanes.     

Long-range electrostatic contributions to the many-body expansion of molecular potentials

A new approach is proposed to the introduction of long range electrostatic terms in the many-body expansion of the molecular potential. The method has been applied to the HO₂ and H₂F₂ potentials.     

On the determination of the long-range form of the interatomic potential from quasi-bound levels

Calculations have been made on the quasi-bound (QB) vibrational levels of BeH and HgH to test the hypothesis that the position of such levels provides an accurate method of determining the form of the long range part of the interatomic potential and the dissociation energy. It is found that if the potential is required to join the spectroscopic RKR potential at some point r _sp then it is only for low J values that the positions of the QB levels are sensitive to the long range part of the potential. It is concluded that the available data on BeH and HgH does not allow an accurate estimate of the long range potential.     

Thin film adhesion modification by MeV ion beams: A model based on ion track concepts

Abstract

A semi-empirical model, based on concepts used to explain the process of track formation in insulators, has been applied to the experimental observation of improved film adhesion produced by MeV ion irradiation. Good agreement is obtained with experimental data for the system of gold film on native oxides of tantalum. The model uses a single free parameter, e ₀, which represents the threshold energy density for the process responsible for the improved bonding. The significance of this parameter is discussed in terms of possible ionisation induced interface phenomena.     

The potential energy surface for the lowest quartet state of H3

SCF MO calculations with CI are carried out on the quartet state of H₃ using an extended (4s, 2p STO) basis and all single and double excitations. The ratio of 3-body to 2-body contributions to the potential at short distance is similar in the two calculations, and at 10 a ₀ the ratio is adequately described by Axilrod-Teller theory.     

新型BrФnsted酸性离子液体的合成与表征

制备了五种对水稳定性好、带-SO3H官能团的磺酸类BrФnsted酸离子液体,用核磁共振(NMR)、红外光谱(IR)、电喷雾质谱(ESI-MS)、热重分析(TG)等表征手段对制备的离子液体进行了表征。结果表明,制备的离子液体与预期设计的结构一致,离子液体纯度大于95%;热重分析发现离子液体具有高的热稳定性和较宽的液态范围,其分解温度均高于300℃;五种离子液体均存在四种离子存在形式,H 可以单独以离子形式存在,并不是通常所认为的仅有两种离子存在形式。另外,研究了离子液体在常用溶剂中的溶解性,发现制备的离子液体易溶于水、甲醇,不溶于乙醚、甲苯和乙酸乙酯。