A brief account of the applications of light scattering spectroscopy to the study of the dynamic properties of dilute macromolecular solutions is presented. In experiments of this type, light is scattered by thermal fluctuations of the molecules in solution about equilibrium. When the circumstances permit, light scattering may be used to study translational diffusion, rotational diffusion, intramolecular structural relaxation processes, and chemical reaction rate constants of macromolecules in dilute solution.
{"title":"Light scattering spectra and dynamic properties of macromolecular solutions","authors":"R. Pecora","doi":"10.1039/DF9704900222","DOIUrl":"https://doi.org/10.1039/DF9704900222","url":null,"abstract":"A brief account of the applications of light scattering spectroscopy to the study of the dynamic properties of dilute macromolecular solutions is presented. In experiments of this type, light is scattered by thermal fluctuations of the molecules in solution about equilibrium. When the circumstances permit, light scattering may be used to study translational diffusion, rotational diffusion, intramolecular structural relaxation processes, and chemical reaction rate constants of macromolecules in dilute solution.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"11 1","pages":"222-227"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78674712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The spectral distribution of slow neutrons scattered at low angles by straight chain hydrocarbon liquids has been measured. For pentane, measurements were made at six different points in PVT space, and the data analyzed by comparison with various models. Properties studied include the diffusion coefficient, the activation energy for diffusion, the time for a diffusive step, the size of a proton's thermal cloud and the spectral density for low frequency (∼1012 Hz) modes of motion. The diffusion data agree well with those obtained by other techniques but the magnitude of the diffusive step time is not well determined for these liquids. A pronounced peak in the low frequency region of the spectral density function has been discovered, and may be associated with short time local bonding between molecules.
{"title":"Low frequency molecular modes in liquid hydrocarbons","authors":"P. A. Egelstaff, D. Harris","doi":"10.1039/DF9704900193","DOIUrl":"https://doi.org/10.1039/DF9704900193","url":null,"abstract":"The spectral distribution of slow neutrons scattered at low angles by straight chain hydrocarbon liquids has been measured. For pentane, measurements were made at six different points in PVT space, and the data analyzed by comparison with various models. Properties studied include the diffusion coefficient, the activation energy for diffusion, the time for a diffusive step, the size of a proton's thermal cloud and the spectral density for low frequency (∼1012 Hz) modes of motion. The diffusion data agree well with those obtained by other techniques but the magnitude of the diffusive step time is not well determined for these liquids. A pronounced peak in the low frequency region of the spectral density function has been discovered, and may be associated with short time local bonding between molecules.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"64 1","pages":"193-207"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80340832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The structure of a simple liquid is determined primarily by the repulsive forces between the molecules. The effects of the attractive forces can be found by perturbation treatments, of which that of van der Waals is the prototype, and that of Barker and Henderson the most recent. The repulsive forces are equally important in determining the structures of mixtures of spherical molecules of different sizes—structures which are quite different from those found in the unmixed liquids. Recent Monte Carlo calculations by Singer can be used as a standard by which theories of mixtures can be judged, and it is shown that the only adequate theories are those which do justice to this difference in structures. It is suggested that the shape of molecules is often of less importance than their size in determining the free energy, and hence that theories of solutions of n-alkanes or of linear polymers do not, in their results, differ greatly from those of mixtures of spherical molecules of different sizes.
{"title":"Introductory. Structure and properties of simple liquids and solutions: a review","authors":"J. Rowlinson","doi":"10.1039/DF9704900030","DOIUrl":"https://doi.org/10.1039/DF9704900030","url":null,"abstract":"The structure of a simple liquid is determined primarily by the repulsive forces between the molecules. The effects of the attractive forces can be found by perturbation treatments, of which that of van der Waals is the prototype, and that of Barker and Henderson the most recent. The repulsive forces are equally important in determining the structures of mixtures of spherical molecules of different sizes—structures which are quite different from those found in the unmixed liquids. Recent Monte Carlo calculations by Singer can be used as a standard by which theories of mixtures can be judged, and it is shown that the only adequate theories are those which do justice to this difference in structures. It is suggested that the shape of molecules is often of less importance than their size in determining the free energy, and hence that theories of solutions of n-alkanes or of linear polymers do not, in their results, differ greatly from those of mixtures of spherical molecules of different sizes.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"37 2","pages":"30-42"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72745298","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Simmons, P. B. Macedo, A. Napolitano, W. Haller
Results from viscosity measurements conducted both above and below the liquid-liquid phase transition of a series of molten oxide glasses are reported in order to analyze the effect of supercritical composition fluctuations on viscous flow, and to investigate the mechanisms of phase separation. Measurements of four oxide mixtures with similar high temperature structures and widely different critical temperatures, revealed an anomalous increase in viscosity at temperatures above the critical point. The anomalous increase occurs when large composition fluctuations characterizing the critical point are present. The effect is explained in terms of an interaction between viscous flow and the supercritical fluctuations through the structural relaxation process. An analysis of this interaction is presented.Measurements conducted at temperatures slightly below the critical point of one of these glasses indicate that the microstructure resulting from the phase separation is highly sensitive to the preceding heat-treatment. Phase separation by the formation of isolated spheres of the silica-rich component is identified a few degrees below the critical point. Further measurements of viscosity by a fibre elongation method, conducted far below the critical temperature, are reported in order to analyze the growth mechanisms occurring in the separated phases. In this case, the rearrangement stage of phase separation is characterized by a growing interconnected structure.
{"title":"Investigation of liquid-liquid phase transitions in oxide melts by viscosity measurements","authors":"J. Simmons, P. B. Macedo, A. Napolitano, W. Haller","doi":"10.1039/DF9705000155","DOIUrl":"https://doi.org/10.1039/DF9705000155","url":null,"abstract":"Results from viscosity measurements conducted both above and below the liquid-liquid phase transition of a series of molten oxide glasses are reported in order to analyze the effect of supercritical composition fluctuations on viscous flow, and to investigate the mechanisms of phase separation. Measurements of four oxide mixtures with similar high temperature structures and widely different critical temperatures, revealed an anomalous increase in viscosity at temperatures above the critical point. The anomalous increase occurs when large composition fluctuations characterizing the critical point are present. The effect is explained in terms of an interaction between viscous flow and the supercritical fluctuations through the structural relaxation process. An analysis of this interaction is presented.Measurements conducted at temperatures slightly below the critical point of one of these glasses indicate that the microstructure resulting from the phase separation is highly sensitive to the preceding heat-treatment. Phase separation by the formation of isolated spheres of the silica-rich component is identified a few degrees below the critical point. Further measurements of viscosity by a fibre elongation method, conducted far below the critical temperature, are reported in order to analyze the growth mechanisms occurring in the separated phases. In this case, the rearrangement stage of phase separation is characterized by a growing interconnected structure.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"12 1","pages":"155-165"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90640182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Interactions between electrons are likely to play an important role in certain transport properties of disordered semiconductors, particularly where these properties depend on electrons in localized states. A working classification of these interactions into intra-site interactions, inter-site interactions and polarization, is made. The first class is believed to affect primarily the transport properties o carriers around the mobility gap, by introducing two-electron wave functions into this region. The second class can introduce an activation energy into the d.c. hopping conductivity at very low temperatures, affect the thermo-electric power, and increase noticeably the a.c. hopping conductivity above a certain frequency. The third class may reduce the activation energy of the d.c. conductivity; a reduction to zero is theoretically possible. Instances where some of the above effects may have been observed are cited.
{"title":"Effect of carrier-carrier interactions on some transport properties in disordered semiconductors","authors":"M. Pollak","doi":"10.1039/DF9705000013","DOIUrl":"https://doi.org/10.1039/DF9705000013","url":null,"abstract":"Interactions between electrons are likely to play an important role in certain transport properties of disordered semiconductors, particularly where these properties depend on electrons in localized states. A working classification of these interactions into intra-site interactions, inter-site interactions and polarization, is made. The first class is believed to affect primarily the transport properties o carriers around the mobility gap, by introducing two-electron wave functions into this region. The second class can introduce an activation energy into the d.c. hopping conductivity at very low temperatures, affect the thermo-electric power, and increase noticeably the a.c. hopping conductivity above a certain frequency. The third class may reduce the activation energy of the d.c. conductivity; a reduction to zero is theoretically possible. Instances where some of the above effects may have been observed are cited.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"71 1","pages":"13-19"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86315673","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In vitreous silica, which has been compacted by irradiation with fast neutrons, the ultrasonic absorption, the excess heat capacity and the magnitude of the negative coefficient of thermal expansion decrease. In this work we report measurements of the far infra-red absorption and Raman scattering in such neutron compacted silica. These results are correlated with new measurements of ultrasonic absorption and thermal expansion in the same material. The results are consistent with an interpretation based on a decrease in the number of low-frequency modes.
{"title":"Raman scattering and far infra-red absorption in neutron compacted silica","authors":"R. Stolen, J. T. Krause, C. Kurkjian","doi":"10.1039/DF9705000103","DOIUrl":"https://doi.org/10.1039/DF9705000103","url":null,"abstract":"In vitreous silica, which has been compacted by irradiation with fast neutrons, the ultrasonic absorption, the excess heat capacity and the magnitude of the negative coefficient of thermal expansion decrease. In this work we report measurements of the far infra-red absorption and Raman scattering in such neutron compacted silica. These results are correlated with new measurements of ultrasonic absorption and thermal expansion in the same material. The results are consistent with an interpretation based on a decrease in the number of low-frequency modes.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"61 1","pages":"103-107"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84570245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The problem of immiscibility in glasses is reviewed. After defining the sub-liquidus immiscibility and considering the stability regions within a miscibility gap, the dynamics of initial clustering are discussed. The distinction between nucleation and growth, spinodal decomposition and coarsening processes is emphasized. Experimental studies of phase separation corresponding to the above mechanisms are presented and, in particular, the possibility of verifying Cahn's theory is discussed. New results from the supercritical region enable the initial condition after quench to be assessed. Finally, the influence of demixing on crystallization is examined and the possibility of thermodynamical blocking of a stable phase indicated.
{"title":"Phase-separated systems","authors":"J. Zarzycki","doi":"10.1039/DF9705000122","DOIUrl":"https://doi.org/10.1039/DF9705000122","url":null,"abstract":"The problem of immiscibility in glasses is reviewed. After defining the sub-liquidus immiscibility and considering the stability regions within a miscibility gap, the dynamics of initial clustering are discussed. The distinction between nucleation and growth, spinodal decomposition and coarsening processes is emphasized. Experimental studies of phase separation corresponding to the above mechanisms are presented and, in particular, the possibility of verifying Cahn's theory is discussed. New results from the supercritical region enable the initial condition after quench to be assessed. Finally, the influence of demixing on crystallization is examined and the possibility of thermodynamical blocking of a stable phase indicated.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"8 1","pages":"122-134"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84574738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A series of transparent homogeneous amorphous solids between GeO2 and GeO has been prepared by rapid quenching of liquids and by vapour deposition. Density and refractive index increase smoothly with increasing Ge/O ratio and provide a useful index of composition. Glasses in the range GeO–GeO1.85 undergo a rapid exothermic transformation when heated above 400°C accompanied by a pronounced blackening, an increase in refractive index, and slight decrease in density. Electron microscopy and diffraction results indicate that the transformation involves the precipitation on a 50–100 A scale of an amorphous tetrahedrally coordinated Ge-rich phase. The interconnected microstructure so produced is suggestive of spinodal decomposition. A transitional region near GeO1.9 is characterized by sluggish phase separation kinetics and a dispersed particle morphology suggestive of a nucleation and growth precipitation mechanism. Glasses in the range GeO1.9–GeO2 show no evidence for phase separation.
{"title":"Phase separation in GeO–GeO2 glasses","authors":"John Philip de Neufville, D. Turnbull","doi":"10.1039/DF9705000182","DOIUrl":"https://doi.org/10.1039/DF9705000182","url":null,"abstract":"A series of transparent homogeneous amorphous solids between GeO2 and GeO has been prepared by rapid quenching of liquids and by vapour deposition. Density and refractive index increase smoothly with increasing Ge/O ratio and provide a useful index of composition. Glasses in the range GeO–GeO1.85 undergo a rapid exothermic transformation when heated above 400°C accompanied by a pronounced blackening, an increase in refractive index, and slight decrease in density. Electron microscopy and diffraction results indicate that the transformation involves the precipitation on a 50–100 A scale of an amorphous tetrahedrally coordinated Ge-rich phase. The interconnected microstructure so produced is suggestive of spinodal decomposition. A transitional region near GeO1.9 is characterized by sluggish phase separation kinetics and a dispersed particle morphology suggestive of a nucleation and growth precipitation mechanism. Glasses in the range GeO1.9–GeO2 show no evidence for phase separation.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"26 1","pages":"182-190"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81756288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
W. Stockmayer, W. Gobush, Y. Chikahisa, D. K. Carpenter
The behaviour of the Zimm model for flexible chain dynamics is illustrated by the dielectric response for arbitrary field strength and by a calculation of the intrinsic viscosity from an appropriate time correlation function. The stochastic dynamics of a chain with constant bond lengths and weak correlations between adjacent bond directions are developed and applied to the dielectric experiment. Introduction of rotational diffusion in parallel to local conformational changes appears to offer a useful approach to the problem of internal viscosity.
{"title":"Dynamic properties of solutions. Models for chain molecule dynamics in dilute solution","authors":"W. Stockmayer, W. Gobush, Y. Chikahisa, D. K. Carpenter","doi":"10.1039/DF9704900182","DOIUrl":"https://doi.org/10.1039/DF9704900182","url":null,"abstract":"The behaviour of the Zimm model for flexible chain dynamics is illustrated by the dielectric response for arbitrary field strength and by a calculation of the intrinsic viscosity from an appropriate time correlation function. The stochastic dynamics of a chain with constant bond lengths and weak correlations between adjacent bond directions are developed and applied to the dielectric experiment. Introduction of rotational diffusion in parallel to local conformational changes appears to offer a useful approach to the problem of internal viscosity.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"1 1","pages":"182-192"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78812942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A series of measurements of Hall effect, thermoelectric power and electrical conductivity have been performed on the vitreous CdGexAs2 having a Ge content of 0.2, 0.3, 0.4, 0.6 and 1 mol respectively. The electrical conductivity has an exponential behaviour in the temperature range 185–500 K only for the 0.6 and 1 mol composition. It deviates from the exponential behaviour at lower temperatures for the 0.2, 0.3 and 0.4 compositions. The thermoelectric power is positive for CdGe0.2As2, negative for CdGe0.6As2 and CdGe1.0As2, whereas it changes sign for CdGe0.3As2 and CdGe0.4As2. The Hall coefficient is negative for alll compositions except for the CdGe1.0As2. The Hall mobilities differ widely for the different compositions and have the values of 1.5 × 10–2 to 1.3 × 10–1 cm2 V–1 s–1 at room temperature.
{"title":"Hall effect, thermoelectric power and electrical conductivity measurements in vitreous CdGexAs2","authors":"R. Callaerts, M. Denayer, F. Hashmi, P. Nagels","doi":"10.1039/DF9705000027","DOIUrl":"https://doi.org/10.1039/DF9705000027","url":null,"abstract":"A series of measurements of Hall effect, thermoelectric power and electrical conductivity have been performed on the vitreous CdGexAs2 having a Ge content of 0.2, 0.3, 0.4, 0.6 and 1 mol respectively. The electrical conductivity has an exponential behaviour in the temperature range 185–500 K only for the 0.6 and 1 mol composition. It deviates from the exponential behaviour at lower temperatures for the 0.2, 0.3 and 0.4 compositions. The thermoelectric power is positive for CdGe0.2As2, negative for CdGe0.6As2 and CdGe1.0As2, whereas it changes sign for CdGe0.3As2 and CdGe0.4As2. The Hall coefficient is negative for alll compositions except for the CdGe1.0As2. The Hall mobilities differ widely for the different compositions and have the values of 1.5 × 10–2 to 1.3 × 10–1 cm2 V–1 s–1 at room temperature.","PeriodicalId":11262,"journal":{"name":"Discussions of The Faraday Society","volume":"1 1","pages":"27-34"},"PeriodicalIF":0.0,"publicationDate":"1970-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76770818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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