摘要:

The ‘potential distribution’ expressions derived by Widom for the pressure and chemical potential of a fluid are developed for the special case of a hard-sphere fluid. The exact equations produced are closely related to those used in Scaled Particle Theory. They have been used to determine the chemical potential of hard-sphere fluids over the reduced density range 0·1 ⩽σ3ρ⩽ 0·8 by means of Monte Carlo sampling. The chemical potential so obtained is in excellent agreement with that found by integrating over pressure as a function of volume. It is found, however, that the chemical potential is considerably more dependent on the sample size than the pressure.

ISSN:0026-8976    

DOI:10.1080/00268977400102551

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The spectrum of an oriented AA′XX′ spin system can be analysed to give only the parameters δAX,JAA′,TAA′zz,JXX′,TXX′zzand the combinations (JAX+JAX′+ 2TAXzz+ 2TAX′zz) and (JAX-JAX′+ 2TAXzz- 2TAX′zz). By controlled, slow sample rotation it is possible to determine all these parameters separately, and some of their relative signs. Application of this technique tocis-difluoroethylene confirms the signs of the coupling constants determined by Baldeschwieleret al.The dipolar couplings forcis-difluoroethylene are compared with values calculated assuming the geometry as determined from microwave spectroscopy and including the effects of harmonic vibrations.

ISSN:0026-8976    

DOI:10.1080/00268977400102561

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Using a perturbation expansion of the transition operatorT, a scattering theory of one and two-photon processes is developed. Distinction is made between Franck-Condon and Herzberg-Teller effects. The influence of each effect is analysed for vibrational and electronic absorption and finally for Raman scattering.

ISSN:0026-8976    

DOI:10.1080/00268977400102571

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Equations of Hartree-Fock type are formulated for a many-electron system described by a wave function containing any number of open and closed shells. The solutions define ‘optimal orbitals’ which minimize theaverageenergy of the states of a configuration in which each shell contains a specified number of electrons. Analogues of the Koopmans theorem are constructed.

ISSN:0026-8976    

DOI:10.1080/00268977400102581

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

A new formulation of the two-by-two rotation method valid for the MC SCF theory of closed-shell systems is given. The method is applied to H2, LiH, BeH2, CH4, H2O and HF.

ISSN:0026-8976    

DOI:10.1080/00268977400102591

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

X-irradiation of single crystals of methylene diphosphonic acid gives rise to E.S.R. spectra which have been assigned to (OH)2(O)P-ĊH2and

ISSN:0026-8976    

DOI:10.1080/00268977400102601

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The mean spherical model is solved analytically for mixtures of dipolar fluids. The components are identified by different but additive molecular radii and different magnitudes of the dipole moment. The direct and indirect correlation functions are found to be functionally dependent on the corresponding hard-sphere functions calculated at certain adjusted densities. Equations for the parameters concerned in calculating such densities are given. The reduction to the equal radii case follows immediately from this analysis.

ISSN:0026-8976    

DOI:10.1080/00268977400102611

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

A new method for derivation of symmetry groups of non-rigid molecules is presented, based on the concept of isometry of nuclear configurations defined by a certain number of internal (structural) coordinates. The substitution group of the internal coordinates interrelating isometric nuclear configurations generates the internal isometric group by both permutations and intransitive imprimitive substitution groups, and together with the covering group it generates the full isometric group. Examples for these groups are given. It is shown that the rotation-internal motion hamiltonian is symmetric with respect to the isometric group. The relation between various approaches to the isometric group is investigated; the role of automorphisms is pointed out. The new approach is shown to give a self-consistent procedure for the quantum mechanical problem associated with the rotation-internal motion hamiltonian.

ISSN:0026-8976    

DOI:10.1080/00268977400102621

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The Raman spectra of chlorine and bromine crystals have been observed at low temperature. Calculations of external frequencies show that the atom-atom interaction is inadequate to explain the spectra of halogen crystals. A charge-transfer term was included in the intermolecular potential to take account of a specific interaction, and the external frequencies calculated with this modified potential agree well with the spectroscopic data. The effect of temperature on lattice frequencies has been estimated, showing disagreement between experimental and theoretical values at high temperature. This disagreement is explained as an anharmonic effect. Dispersion curves of external and internal modes of vibration using the modified potential are also included.

ISSN:0026-8976    

DOI:10.1080/00268977400102631

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The high-temperature series expansion for the free energy of a lattice of classical permanent dipoles is obtained to order (μ2/T)5, where μ is the dipole moment andTthe temperature. Numerical values of the coefficients in the series are presented for three cubic lattices. Two Padé approximants to the expansion are constructed which exhibit the appropriate low-temperature behaviour of the free energy. These approximants are compared with results of the spherical model for this system, and it is found that the simplest of these gives an accurate assessment of the exact low-temperature behaviour. The Padé approximant results for the free energy also agree quite well with the spherical model results. The implications of these observations for polar fluids are noted. A connection is presented between the free energy and the Clausius-Mossotti function for dipolar lattices. A Padé approximant to the Clausius-Mossotti function which is constructed to satisfy known bounds is found to agree with the spherical model results for this quantity.

ISSN:0026-8976    

DOI:10.1080/00268977400102641

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor