Pub Date : 2002-05-01DOI: 10.1080/13642810208218352
J. Ferrez, Th.M. Lieblin3g
Abstract The distinct element method (DEM) is an approach to modelling and simulation well suited to the study of discontinuous phenomena. By tracking each element individually and dealing explicitly with every interaction among the elements, the DEM allows one to deduce statistical behaviour of the assembly. Realistic simulation of granular materials has largely benefited from this relatively recent approach. In particular, it is now possible to address specific phenomena such as arching effects, flows and packings in three dimensions and to make them observable, which is impossible or at least extremely complicated to achieve with physical experiments. Two major issues arise in the context of DEM: efficient detection of the interactions between the grains and numerical modelling of the physical contacts. This paper focuses on the former by presenting an efficient collision detection scheme for spherical grains of various sizes based on a dynamic three-dimensional Delaunay triangulation. Aside from the theoretical and practical discussion of this scheme, the remaining requirements for a complete DEM simulation are also addressed. Finally, examples are given to illustrate the potential of this approach.
{"title":"Dynamic triangulations for efficient detection of collisions between spheres with applications in granular media simulations","authors":"J. Ferrez, Th.M. Lieblin3g","doi":"10.1080/13642810208218352","DOIUrl":"https://doi.org/10.1080/13642810208218352","url":null,"abstract":"Abstract The distinct element method (DEM) is an approach to modelling and simulation well suited to the study of discontinuous phenomena. By tracking each element individually and dealing explicitly with every interaction among the elements, the DEM allows one to deduce statistical behaviour of the assembly. Realistic simulation of granular materials has largely benefited from this relatively recent approach. In particular, it is now possible to address specific phenomena such as arching effects, flows and packings in three dimensions and to make them observable, which is impossible or at least extremely complicated to achieve with physical experiments. Two major issues arise in the context of DEM: efficient detection of the interactions between the grains and numerical modelling of the physical contacts. This paper focuses on the former by presenting an efficient collision detection scheme for spherical grains of various sizes based on a dynamic three-dimensional Delaunay triangulation. Aside from the theoretical and practical discussion of this scheme, the remaining requirements for a complete DEM simulation are also addressed. Finally, examples are given to illustrate the potential of this approach.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91053987","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}
Pub Date : 2002-05-01DOI: 10.1080/13642810208224370
M. Jung, I. Inoue, H. Nakotte, A. Lacerda
Abstract The magnetic properties of perovskite CaVO3 single crystals have been studied by means of magnetoresistance ρ (T, H) and magnetization M(H) measurements in fields to 18 T. At 2K, the magnetoresistance is positive and a maximum value of Δρ(18T)/ρ(0) = 16.5% is found for H//a. The magnetization exhibits a smooth increase at 2K, reaching values of M(18T) = 0.03μB (formula unit (fu))−1, 0.05,μB fu−1, 0.17/μB fu−1 for H//a, H//b and H//c, respectively. This anisotropy found in M(H) is consistent with that observed for Δρ(H//a) ≥ ρ(H//b) > Δρ(H//c). These results can be interpreted in terms of the field-dependent scattering mechanism of CaVO3.
{"title":"High-field properties of single-crystal CaVO3","authors":"M. Jung, I. Inoue, H. Nakotte, A. Lacerda","doi":"10.1080/13642810208224370","DOIUrl":"https://doi.org/10.1080/13642810208224370","url":null,"abstract":"Abstract The magnetic properties of perovskite CaVO3 single crystals have been studied by means of magnetoresistance ρ (T, H) and magnetization M(H) measurements in fields to 18 T. At 2K, the magnetoresistance is positive and a maximum value of Δρ(18T)/ρ(0) = 16.5% is found for H//a. The magnetization exhibits a smooth increase at 2K, reaching values of M(18T) = 0.03μB (formula unit (fu))−1, 0.05,μB fu−1, 0.17/μB fu−1 for H//a, H//b and H//c, respectively. This anisotropy found in M(H) is consistent with that observed for Δρ(H//a) ≥ ρ(H//b) > Δρ(H//c). These results can be interpreted in terms of the field-dependent scattering mechanism of CaVO3.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86270921","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}
Pub Date : 2002-05-01DOI: 10.1080/13642810208218354
A. Ślebarski, M. Maple, E. J. Freeman, C. Sirvent, M. Radłowska, A. Jezierski, E. Granado, Q. Huang, J. W. Lynn
Abstract Electrical resistivity ρ, magnetic susceptibility χ, specific heat C, X-ray photoelectron spectroscopy (XPS) and X-ray and neutron diffraction measurements were made on the compound CeRhSn. The measurements reveal an enhancement of the electronic specific heat coefficient γ = C(T)/T ≈ 160 mJ mol−1 K−2 at about 1 K and non-Fermi-liquid-like temperature dependences ρ(T) α T 0.75 and χ(T) α T −0.5 at low temperatures. At high temperatures, the physical properties indicate Kondo-intermediate-valence behaviour. The XPS measurements are consistent with a Ce valence of 3.07. The neutron diffraction measurements reveal anomalies in the planar Ce-Rh and Ce-Ce bond distances in the vicinity of 100 K which are apparently associated with the Ce valence instability in CeRhSn.
{"title":"Strongly correlated electron behaviour in the compound CeRhSn","authors":"A. Ślebarski, M. Maple, E. J. Freeman, C. Sirvent, M. Radłowska, A. Jezierski, E. Granado, Q. Huang, J. W. Lynn","doi":"10.1080/13642810208218354","DOIUrl":"https://doi.org/10.1080/13642810208218354","url":null,"abstract":"Abstract Electrical resistivity ρ, magnetic susceptibility χ, specific heat C, X-ray photoelectron spectroscopy (XPS) and X-ray and neutron diffraction measurements were made on the compound CeRhSn. The measurements reveal an enhancement of the electronic specific heat coefficient γ = C(T)/T ≈ 160 mJ mol−1 K−2 at about 1 K and non-Fermi-liquid-like temperature dependences ρ(T) α T 0.75 and χ(T) α T −0.5 at low temperatures. At high temperatures, the physical properties indicate Kondo-intermediate-valence behaviour. The XPS measurements are consistent with a Ce valence of 3.07. The neutron diffraction measurements reveal anomalies in the planar Ce-Rh and Ce-Ce bond distances in the vicinity of 100 K which are apparently associated with the Ce valence instability in CeRhSn.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84121561","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}
Pub Date : 2002-04-30DOI: 10.1080/13642810210127011
P. Kumar, A. Saxena
Abstract The well-known scaling laws relating critical exponents in a second-order phase transition have been generalized to the case of an arbitrarily higher-order phase transition. In a higher-order transition, such as suggested for the superconducting transition in Ba0.6K0.4BiO3 and in Bi2Sr2CaCu2O8, there are singularities in higher-order derivatives of the free energy. A relation between exponents of different observables has been found, regardless of whether the exponents are classical (mean-field theory; no fluctuations; integer order of a transition) or not (fluctuation effects included). We also comment on the phase transition in a thin film.
{"title":"Thermodynamics of a higher-order phase transition: Scaling exponents and scaling laws","authors":"P. Kumar, A. Saxena","doi":"10.1080/13642810210127011","DOIUrl":"https://doi.org/10.1080/13642810210127011","url":null,"abstract":"Abstract The well-known scaling laws relating critical exponents in a second-order phase transition have been generalized to the case of an arbitrarily higher-order phase transition. In a higher-order transition, such as suggested for the superconducting transition in Ba0.6K0.4BiO3 and in Bi2Sr2CaCu2O8, there are singularities in higher-order derivatives of the free energy. A relation between exponents of different observables has been found, regardless of whether the exponents are classical (mean-field theory; no fluctuations; integer order of a transition) or not (fluctuation effects included). We also comment on the phase transition in a thin film.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75221735","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}
Pub Date : 2002-04-01DOI: 10.1080/13642810208224363
E. Cattaruzza, G. Battaglin, F. Gonella, R. Polloni, G. Mattei, C. Maurizio, P. Mazzoldi, C. Sada, M. Montagna, C. Tosello, M. Ferrari
Abstract Metal nanocluster composite glasses (MNCGs) have been the subject of both experimental and theoretical investigation because of their peculiar optical properties. In particular, the enhanced third-order optical nonlinearity could be exploited in the all-optical switching device technology. Nevertheless, several factors such as thermal stability, wavelength tunability, response time regime, recycling frequency, laser-induced damage and optical absorption come into play in the definition of the material suitability. In this work, we present some results on MNCG films prepared by ion implantation. Nonlinear refractive index values are also presented for rf sputtered films, evidencing the presence of thermal nonlinearity in the optical response. Figures of merit that must be satisfied for ultrafast all-optical switching application of MNCGs are evaluated for this composite.
{"title":"On the optical absorption and nonlinearity of silica films containing metal nanoparticles","authors":"E. Cattaruzza, G. Battaglin, F. Gonella, R. Polloni, G. Mattei, C. Maurizio, P. Mazzoldi, C. Sada, M. Montagna, C. Tosello, M. Ferrari","doi":"10.1080/13642810208224363","DOIUrl":"https://doi.org/10.1080/13642810208224363","url":null,"abstract":"Abstract Metal nanocluster composite glasses (MNCGs) have been the subject of both experimental and theoretical investigation because of their peculiar optical properties. In particular, the enhanced third-order optical nonlinearity could be exploited in the all-optical switching device technology. Nevertheless, several factors such as thermal stability, wavelength tunability, response time regime, recycling frequency, laser-induced damage and optical absorption come into play in the definition of the material suitability. In this work, we present some results on MNCG films prepared by ion implantation. Nonlinear refractive index values are also presented for rf sputtered films, evidencing the presence of thermal nonlinearity in the optical response. Figures of merit that must be satisfied for ultrafast all-optical switching application of MNCGs are evaluated for this composite.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80660240","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}
Pub Date : 2002-04-01DOI: 10.1080/13642810208224361
R. Almeida, P. J. Morais, A. Marques
Abstract Sol-gel processing is becoming one of the cheapest and most versatile methods for the fabrication of passive and active planar waveguides for integrated optics, in particular for the silica-on-silicon type. The present paper focuses on some recent work in our group on both passive and active (Er3+-doped) silica–titania inorganic and hybrid waveguides, considering in detail their densification behaviour, structure and optical properties. Recent advanced topics, such as nanocrystalline active waveguides prepared by by sol–gel method, are also addressed. The main results to be presented will deal first with the structural evolution during the densification of inorganic and hybrid silica-titania waveguides. Then, the fluorescence behaviour of active waveguides, doped with Er3+ ions, will also be described. And finally silver co-doped nanocrystalline waveguides, will be considered in detail, with particular emphasis on, firstly, the influence of preparation conditions on optical properties such as the visible and infrared absorption spectra, including the characterization of the surface plasmon resonances of the silver nanoparticles by visible spectroscopy as well as the 1.5 μm fluorescence lifetime and, secondly, the nature of the chemical environment of the erbium and silver ions, before the thermally induced nanocrystallite precipitation and during the course of film densification.
{"title":"Planar waveguides for integrated optics prepared by sol–gel methods","authors":"R. Almeida, P. J. Morais, A. Marques","doi":"10.1080/13642810208224361","DOIUrl":"https://doi.org/10.1080/13642810208224361","url":null,"abstract":"Abstract Sol-gel processing is becoming one of the cheapest and most versatile methods for the fabrication of passive and active planar waveguides for integrated optics, in particular for the silica-on-silicon type. The present paper focuses on some recent work in our group on both passive and active (Er3+-doped) silica–titania inorganic and hybrid waveguides, considering in detail their densification behaviour, structure and optical properties. Recent advanced topics, such as nanocrystalline active waveguides prepared by by sol–gel method, are also addressed. The main results to be presented will deal first with the structural evolution during the densification of inorganic and hybrid silica-titania waveguides. Then, the fluorescence behaviour of active waveguides, doped with Er3+ ions, will also be described. And finally silver co-doped nanocrystalline waveguides, will be considered in detail, with particular emphasis on, firstly, the influence of preparation conditions on optical properties such as the visible and infrared absorption spectra, including the characterization of the surface plasmon resonances of the silver nanoparticles by visible spectroscopy as well as the 1.5 μm fluorescence lifetime and, secondly, the nature of the chemical environment of the erbium and silver ions, before the thermally induced nanocrystallite precipitation and during the course of film densification.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87481132","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}
Pub Date : 2002-04-01DOI: 10.1080/13642810208224362
G. Righini, M. Brenci, M. A. Forastiere, S. Pelli, G. Ricci, G. N. Conti, N. Peyghambarian, M. Ferrari, M. Montagna
Abstract Rare-earth-doped (Er−, Yb− and Er+ Yb-doped) silica glasses have been produced and characterized. Their spectroscopic properties have been assessed and optical amplification devices have been produced therefrom and characterized.
{"title":"Rare-earth-doped glasses and ion-exchanged integrated optical amplifiers and lasers","authors":"G. Righini, M. Brenci, M. A. Forastiere, S. Pelli, G. Ricci, G. N. Conti, N. Peyghambarian, M. Ferrari, M. Montagna","doi":"10.1080/13642810208224362","DOIUrl":"https://doi.org/10.1080/13642810208224362","url":null,"abstract":"Abstract Rare-earth-doped (Er−, Yb− and Er+ Yb-doped) silica glasses have been produced and characterized. Their spectroscopic properties have been assessed and optical amplification devices have been produced therefrom and characterized.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87869297","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}
Pub Date : 2002-04-01DOI: 10.1080/13642810208224365
O. Pilla, A. Fontana, P. Freire, A. Teixeira
Abstract Brillouin experiments on vitreous yttrium-phosphate glass under pressures up to 7GPa obtained using a diamond anvil cell are reported. Irreversible changes occur as a function of pressure and are interpreted as an indication of a new polymorph of the original glass. The results are compared with the experimental data available for a series of different glassy systems. The observed Brillouin frequency shift under pressure relative to longitudinal waves is assigned to a rearrangement of PO4 tetrahedra. A mechanism accounting for the pressure-induced transition in glasses is proposed.
{"title":"High-pressure Brillouin scattering from vitreous(Y2O3)0.27(P2O5)0.73","authors":"O. Pilla, A. Fontana, P. Freire, A. Teixeira","doi":"10.1080/13642810208224365","DOIUrl":"https://doi.org/10.1080/13642810208224365","url":null,"abstract":"Abstract Brillouin experiments on vitreous yttrium-phosphate glass under pressures up to 7GPa obtained using a diamond anvil cell are reported. Irreversible changes occur as a function of pressure and are interpreted as an indication of a new polymorph of the original glass. The results are compared with the experimental data available for a series of different glassy systems. The observed Brillouin frequency shift under pressure relative to longitudinal waves is assigned to a rearrangement of PO4 tetrahedra. A mechanism accounting for the pressure-induced transition in glasses is proposed.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81439817","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}
Pub Date : 2002-04-01DOI: 10.1080/13642810208224364
M. Mortier
Abstract We report results of controlled devitrification of rare-earth-doped glasses made in order to improve the initial spectroscopic properties of the as-melted glass to obtain crystal-like properties. This study is made to allow the design of reduced-size photonic devices owing to the use of more efficient active materials. The main possibilities of devitrification of glasses are evaluated in two glassy systems and compared. The key point is the choice of the glass composition allowing partial crystallization during thermal treatments adapted to the thermal stability of the material. A strong improvement in the spectroscopic properties of the rare-earth ions has been obtained in a heterogeneously nucleated glass (GeO2–PbO–PbF2). The final glass-ceramic is ultratransparent with weak additional losses mainly in the short-wavelength region. Another possibility has been evaluated through the spinodal decomposition of a fluorozirconate glass (ZrF4–LaF3–AlF3–GaF3–ErF3). Its spectroscopic properties are also mostly crystal like with only a weak scattering-induced reduction of transparency.
{"title":"Between glass and crystal: Glass–ceramics, a new way for optical materials","authors":"M. Mortier","doi":"10.1080/13642810208224364","DOIUrl":"https://doi.org/10.1080/13642810208224364","url":null,"abstract":"Abstract We report results of controlled devitrification of rare-earth-doped glasses made in order to improve the initial spectroscopic properties of the as-melted glass to obtain crystal-like properties. This study is made to allow the design of reduced-size photonic devices owing to the use of more efficient active materials. The main possibilities of devitrification of glasses are evaluated in two glassy systems and compared. The key point is the choice of the glass composition allowing partial crystallization during thermal treatments adapted to the thermal stability of the material. A strong improvement in the spectroscopic properties of the rare-earth ions has been obtained in a heterogeneously nucleated glass (GeO2–PbO–PbF2). The final glass-ceramic is ultratransparent with weak additional losses mainly in the short-wavelength region. Another possibility has been evaluated through the spinodal decomposition of a fluorozirconate glass (ZrF4–LaF3–AlF3–GaF3–ErF3). Its spectroscopic properties are also mostly crystal like with only a weak scattering-induced reduction of transparency.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90395420","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}
Pub Date : 2002-04-01DOI: 10.1080/13642810208224356
S. Capaccioli, M. Lucchesi, R. Casalini, S. Presto, P. Rolla, M. T. Viciosa, S. Corezzi, D. Fioretto
Abstract The pressure and temperature behaviours of the structural relaxation time in glass-forming systems can be well described by a new equation, based on the Adam-Gibbs model, where the configurational entropy has been written in terms of the excess heat capacity and the molar thermal expansion. An experimental check of this equation was performed on the dynamics of an epoxy compound, investigated by wide-band dielectric spectroscopy (10−2–1010Hz). Six different sets of relaxation data, corresponding to two different conditions, were analysed: firstly, isobaric (atmospheric pressure and 95.5 MPa) with various temperatures down to the supercooled and glassy phases and, secondly, isothermal (at four different temperatures) with changing pressure in the range 0.1–270 MPa. Moreover, the thermal expansion was independently determined from data on the pressure and temperature variations of the volume of the material. From this analysis, the pressure-extended Adam-Gibbs model resulted, which is so suitable for describing the two-dimensional surface τ(T,P) over the whole investigated range of temperatures and pressures that a master curve can be obtained from all the relaxation times if plotted versus a variable related to the configurational entropy directly derived from thermodynamic data.
{"title":"Pressure and temperature dependences of the dynamics of glass formers studied by broad-band dielectric spectroscopy","authors":"S. Capaccioli, M. Lucchesi, R. Casalini, S. Presto, P. Rolla, M. T. Viciosa, S. Corezzi, D. Fioretto","doi":"10.1080/13642810208224356","DOIUrl":"https://doi.org/10.1080/13642810208224356","url":null,"abstract":"Abstract The pressure and temperature behaviours of the structural relaxation time in glass-forming systems can be well described by a new equation, based on the Adam-Gibbs model, where the configurational entropy has been written in terms of the excess heat capacity and the molar thermal expansion. An experimental check of this equation was performed on the dynamics of an epoxy compound, investigated by wide-band dielectric spectroscopy (10−2–1010Hz). Six different sets of relaxation data, corresponding to two different conditions, were analysed: firstly, isobaric (atmospheric pressure and 95.5 MPa) with various temperatures down to the supercooled and glassy phases and, secondly, isothermal (at four different temperatures) with changing pressure in the range 0.1–270 MPa. Moreover, the thermal expansion was independently determined from data on the pressure and temperature variations of the volume of the material. From this analysis, the pressure-extended Adam-Gibbs model resulted, which is so suitable for describing the two-dimensional surface τ(T,P) over the whole investigated range of temperatures and pressures that a master curve can be obtained from all the relaxation times if plotted versus a variable related to the configurational entropy directly derived from thermodynamic data.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79793951","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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