ISSN:0005-9021    

DOI:10.1002/bbpc.19850890102

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractComputer simulation results are reported for model Gaussian overlap molecules with orientation independent well depths (GOCE systems) at different anisotropies. A procedure is developed for the comparison of the thermodynamics of these systems with equivalent 12‐6 site‐site systems. Comparison of thermodynamic properties of prolate systems with those for site‐site diatomics showed good agreement, especially at low anisotropies. The structures of these two systems indicated that relative molecular orientations around the T shape are more favored for site‐site diatomics than in the GOCE case. The thermodynamics of the oblate benzene‐like GOCE system (K= 0.50) were studied and results were obtained that do not agree well with the experimental data for liquid benzene. Comparison of the structure of this GOCE system with recent simulations using a six‐centered site‐site potential for benzene showed that the GOCE fluid is less structured than the si

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890103

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractSimple pseudo‐spherical harmonic expansions over non‐spherical surfaces are proposed for two body functions such as pair potentials and pair correlation functions of anisotropic fluids. It is shown that the thermodynamics of fluids with Gaussian overlap potential with constant well depth (GOCE fluids) can be calculated from only the leading terms in the expansions over equipotential surfaces. Resummation of the individual terms in the expansions of pair correlation functions over equipotential surfaces give molecular correlations for specific orientations which agreed very well with the same functions calculated directly during the simulations. These functions are used to bring out some significant differences in the structures of GOCE fluids and equivalent site‐site fluids. Support for this work by a grant from the Chemistry Division of the National Science Foundation is gratefully acknowl

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890104

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractA direct comparison of experimental depolarized Rayleigh spectra of CO2with those obtained by molecular dynamics (MD) simulations at two different statepoints are reported. For the MD simulations a three Lennard‐Jones centres and central point quadrupole moment (3LJC + Q) interaction model has been used. Total depolarized spectra as well as their constituents (a) orientational, (b) collision induced, and (c) cross spectra were calculated for two polarizability models: In the first centre‐centre (C‐C) model the molecular polarizability is placed in the centre of the molecules whereas in the second site‐site (S‐S) model two partial polarizabilities are placed on the O atom sites. At the lower density the spectra resulting from both polarizability models compare well with the experimental spectrum. At the high density both model spectra noticeably deviate from the experimental one: the C‐C model spectrum giving the better description. This result is in contradiction to a previous investigation based on a two Lennard‐Jones centres potential. Thus any assessment of the relative merits of the two polarizability models seem to be premature at this stage since the role played by the interaction potential is not ful

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890105

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractBinary mixtures of nitrogen with ethane and pentane, respectively, were investigated at pressures up to 200 MPa in an optical high‐pressure low‐temperature cell according to the synthetic method. The experimentalp(T)isopleths show that both systems exhibit upper critical solution temperatures (UCST) at high pressures. The resulting critical curves start at the critical point of the pure alkane, respectively. With decreasing temperatures the criticalp(T)curve of the system nitrogen + pentane runs to higher pressures exhibiting a positive curvature whereas the critical curve of the system nitrogen + ethane firstly goes through a slight pressure maximum and minimum successively and then runs steeply to increasing pressures showing a positive curvature, too. The critical curve of the system nitrogen + ethane ends at a critical end point on the three‐phase line lls ((176 ± 2) MPa, (105 ± 0.3) K) where two liquid phases become identical in the presence of solid

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890106

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractA critical test of the additivity rule of the partial molal or molal volume (Ṽ) at constant temperature and pressure, expressed byṼ = αn + βwherenis the carbon number, has been made for a wide range of n‐alkanes at a variety of temperatures and pressures. In the pure liquid state the additivity rule is obeyed approximately well by the higher n‐alkanes but broken by the lower ones having the boiling point close to the temperature of interest, and in solution at infinite dilution it is obeyed much more accurately by both high and low n‐alkanes. These facts indicate that the additivity rule holds more accurately for the configurational partial molal volume than for the partial molal volume itself. The virial theorem for classical fluids is applied here to separate the overall partial molal volume into the translational and configurational components; the translational contribution is proved to be the isothermal compressibility multiplied by the gas constant and temperature. The parameter a decreases slightly and linearly and the parameter β decreases significantly and nonlinearly as temperature is lowered or pressure

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890107

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractThe kinetics of the electron transfer reactions of aquoiron(III) with ferrocene (Fer) and its n‐butyl (BFer), 1,1′‐dimethyl (DMFer) and 1,1′‐di‐n‐butyl (DBFer) derivatives have been studied in the presence of cationic (CTAN) and non‐ionic (Triton X‐100) micelles at 20.0°C and ionic strength 0.02 mol dm−3. Both surfactants inhibit nearly at the same extent the reaction involving a given ferrocene derivative. The rate inhibition depends strongly on the alkyl groups present in the molecule of ferrocene, following the order DBFer>BFer>DMFer>Fer. The binding constants and the contribution of a methylene (or methyl) group of the alkyl substituents to the transfer free energy from water to micelle have been estimated and discussed, suggesting that ferrocenes are locate

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890108

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractAqueous dispersions of multilamellar liposomes of pure lipids and binary lipid mixtures have been investigated by densitometry. It is shown that the employed mechanical oscillator technique is well suited to derive volumetric data of different lipid phases and to characterize the transitions between them. Transition temperatures, widths, volume changes and in some cases also the kinetics can be studied. — For binary lipid alloys temperature‐composition‐phase diagrams can be established. By analysing the thermal expansion a direct comparison with calorimetric data is possible. Finally, an example for a chemically induced phase separation is

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890109

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractThe sorption of Sr by graphitic materials used in high‐temperature gas‐cooled reactors was studied by applying high‐temperature mass spectro‐metry with a Knudsen cell and the isopiestic method. Sorption isotherms were determined for matrix graphite with Sr concentrations between 3.88 · 10−5and 8.85 · 10−2mol kg−1. The sorption enthalpies and partial pressures determined for concentrations greater than 1.5 · 10−4mol kg−1showed many properties of Freundlich isotherms. The evaluated vaporization enthalpies of Sr(e.g. ΔvH01660= 447. 8 ± 7.7 kj mol−1for a Sr concentration of 3.42 · 10−4mol kg−1) indicate a strong chemisorption of Sr by graphite. An exceptionally high sorption capacity for Sr has been observed for nong

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890110

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY

摘要:

AbstractApplying the manometric method, the solubility of hydrogen in alloys Ti1‐xGaxwas studied in the range 0 ≦x≦ 25; 5 · 10−5≦pH2/bar ≦ 1; 773 ≦T/K ≦ 1298. Within the given range ofpandTthe phase diagram of Ti1‐xGaxHrwas investigated for 9 compositionsx. In the range of solid solutions, 0 ≦x≦ 0.11, with increasingxthe range Δrof the hcp phase α‐Ti1‐xGaxHrincreases slightly, whereas the range of the bcc phase β‐Ti1‐xGaxHr, narrows strongly with increasingx. The width Δrof the two phase region α + β is nearly independent ofxand the phase boundary between β‐phase and (β + γ) region shifts with decreasing Δrof the β‐phase to smallerr. In α‐T1‐xGaxHrthe enthalpy of hydrogen solution ΔHHis practically independent ofrbut depends slightly onx, decreasing from ‐46.0 kJ mol−1(x= 0) to ‐46.5 kJ mol−1(x= 0.10). In the bcc phase β‐Ti1‐xGaxHr, ΔHHdecreases markedly from ‐57 kJ mol−1(r→ 0) to ‐70 kJ mol−1(r⇌ 1). ΔHHis independent of the gallium contentxwithin the limits of error. — Assuming a plausible blocking model for the occupancy of interstitial sites in the metal matrix by hydrogen, the excess entropies of dissolved hydrogen were evaluated. In α‐Ti1‐xGaxHran increase of ΔSEHis found with increasingrfrom ‐55 JK−1mol−1(r→0) to ‐53 JK−1mol−1(r= 0.1). ΔSEHdepends much stronger onrin β‐Ti1‐xGaxHr: ΔSEH= ‐70 JK−1mol−1(r→0); ΔSEH= ‐66.5 JK−1mol−1(r= 0.8). There is negligible influence ofxon ΔSEHin both phases. — In the ordered hcp phase α2‐Ti3GaHrthere is an increase of exothermicity compared to α‐Ti1‐xGaxHr. ΔHH(r→ 0) is ‐51.3 kJ mol−1for the ordered phase and it depends onr, increasing to ‐50 kJ mol−1atr⇌ 0.1. ΔSEHfor this phase is independent ofr, ΔSEH

ISSN:0005-9021    

DOI:10.1002/bbpc.19850890111

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1985

数据来源: WILEY