... 56 MJ Clancy et al. / International Journal of Pharmaceutics 105 (1994) 47-56 mechanistic ana... more ... 56 MJ Clancy et al. / International Journal of Pharmaceutics 105 (1994) 47-56 mechanistic analysis and application to poiypeptide deliv-ery. J. Pharm. Sei.. 78 (1989) 370-375. Tyle, P. and Agrawala, P., Drug delivery by phonophoresis. Pharm. Res.. 6 (1989) 355-361. Walker, M ...
The role of defects in matter transport through solid materials is discussed and the nature of th... more The role of defects in matter transport through solid materials is discussed and the nature of the principal types of point and extended defects, as well as the evidence for their existence, is examined. The equations governing the participation of defects in ionic conduction and diffusion are developed from first principles as is the relationship between these processes. The experimental methods available for the measurement of matter transport in solid materials and the techniques used for effective data analyses are described. Finally the current level of knowledge of diffusion processes in a range of different types of solids is reviewed.
It is a truism that the more we learn about anything the more complex that subject becomes. This ... more It is a truism that the more we learn about anything the more complex that subject becomes. This is especially true of our understanding of the exact arrangement of atoms or ions which make up solid materials.The rapid development and improvement of the techniques by which defects solids are detected and characterized, and which form the subject matter of this book, have necessitated constant revision of our concepts of perfect and defective solids. It is, for example, no longer adequate to confine our attention to isolated point defects without also considering their aggregation to form more complex defect centres and eventually even separate phases, their relationship with non-stoichiometry and their interactions with each other and with the linear and planar defects with which they co-exist. Similarly, the precise structural information now available for many materials reveals that non-stoichiometric phases may exist as modulated structures in which the composition may vary in a continuous fashion to yield commensurate, semi-commensurate and incommensur-ate structures. The presence of shear planes also changes the composit-ion of non-stoichiometric phases.
The nature and occurrence of fast-ion conduction (FIC) in solids is described and explained and t... more The nature and occurrence of fast-ion conduction (FIC) in solids is described and explained and the materials in which it is operative, ranging from crystals through amorphous glassy electrolytes to ionically conducting polymeric complexes, are classified. FIC processes in a number of materials which are of particularly technological interest e.g. oxygen ion conductors and glassy and polymeric electrolytes, are discussed in detail. A number of key applications of these materials in solid state ionics and, in particular recently reported progress is also described. The emphasis is on the overall physical properties that are required in the design of a successful optimized material
ABSTRACT Apart from man’s innate need to model and the satisfaction that a good model can bring, ... more ABSTRACT Apart from man’s innate need to model and the satisfaction that a good model can bring, the real purpose of scientific modelling is to increase our understanding of a system. More importantly, it provides the basis from which to move forward to understand more complex systems and to design such new systems for specific applications by making predictions about their properties. Simple ionic solids, such as the alkali and silver halides, some fluoritestructured crystals and binary oxides, provide the most accessible and well-developed testing grounds for the study, both experimental and theoretical, of point defects in crystalline materials. This is because defects in these crystals typically carry a charge different from those on the ions that comprise the normal components of the matrix. Their presence, nature, interactions and movements can therefore be rather easily quantitatively determined through the measurement of readily observed macroscopic properties such as ionic conductivity. These charges can be present whether the defects are intrinsic or extrinsic. Intrinsic defects, such as Schottky or Frenkel defects, are equilibrium thermodynamic defects and exist in all materials because the balance between the enthalpy required for their formation in a perfect lattice and the resulting increase in the entropy of the system gives rise to a minimum in the Gibbs free energy. There is a corresponding equilibrium intrinsic defect concentration at each temperature.
The thermochromism of poly(3-alkylthiophene)s is explained as a buckling of the main chain by tor... more The thermochromism of poly(3-alkylthiophene)s is explained as a buckling of the main chain by torsions around the interring bonds resulting in a dilation of the rc band energy gap. Atomi>tic simulation calculations show that the necessity to preserve translational periodicity imposes restrictions on the permitted torsions. In our model the effect of heating causes a relative shift of adjacent polymLr chains, changing the ring stacking from 'staggered' to 'eclipsed', in which the chains undergo a spontaneous torsion of 20".
Simulating the \hbox{BF}_{4}^{-} -doped poly(3-octylthiophene) lattice by molecular dynamics resu... more Simulating the \hbox{BF}_{4}^{-} -doped poly(3-octylthiophene) lattice by molecular dynamics results in a structure in which dopant ions intercalate as a sandwich between thiophene rings on adjacent polymer chains. The ions occupy sites in channels parallel to the polymer main chain, which retains a high degree of planarity in contrast to the pristine (undoped) polymer. Even when lattice imperfections are created by expanding the cell, Coulomb forces ensure that the intercalation features containing the dopant channels are largely retained. On applying electric fields in the principal directions of the 'perfect lattice' it is found that the ions migrate most readily along the ion-channel directions (the lattice c axis), leaving the lattice undisturbed. Although higher electric fields cause dopant migration to occur perpendicular to the channel directions they destroy the intercalated lattice. In the reduced-order lattice regions substantial motion of the ions are predicted at a critical value of the lattice parameter.
The high-temperature conductivity of pure AgCl has been reexamined with a view to establishing mo... more The high-temperature conductivity of pure AgCl has been reexamined with a view to establishing more precisely the mobility parameters for non-collinear interstitialcy motion of Ag+ interstitials. The possible roles of direct interstitial jumps, Schottky defects, and temperature dependent activation energies has been assessed. Fomulae are given for the activity coefficients of interstitials and vacancies evaluated to O(x2) in an approximation that uses a sphericalized Brillouin zone and inlcudes only the cycle sum contributions. These activity coefficients are compared with those evaluated from the Debye-Huckel formula and their effect on the defect parameters obtained from conductivity data is assessed. Die Hochtemperaturleitfahigkeit von reinem AgCl wurde im Hinblick auf eine genauere Festlegung der Beweglichkeitsparameter fur nicht-kollineare Zwischengitterbewegung von Ag+-Zwischengitterionen erneut uberpruft. Die mogliche Rolle direkter Zwischengitterspriinge, Schottky-Defekte und temperaturabhangiger Aktivierungsenergien wurde abgeschatzt. Es werden Gleichungen fur die Aktivitatskoeffizienten von Zwischengitterteilchen und Leerstellen angegeben, die bis zu O(xz) ausgewertet werden in einer Naherung, welche spharikalisierte Brillouin-Zonen benutzt und nur die Beitrage der Zyklussummen enthalt. Diese Aktivitatskoeffizienten werden mit den nach der Debye-Huckel-Gleichung ausgewerteten verglichen und ihr EinfluB auf die aus den Leitfahigkeitsdaten erhaltenen Defektparameter wird abgeschatzt.
Abstract The conformations of the chains constituting the hydrophilic component of alkyl monolaye... more Abstract The conformations of the chains constituting the hydrophilic component of alkyl monolayers and bilayers are investigated by performing molecular dynamics atomistic simulations on these systems at different temperatures. Several monitoring techniques are used to reveal the chain conformations, including atom pair radial distribution functions, evolutions of the torsional angles over thousands of timesteps, frequency distributions of the torsionl angles and ‘snapshot’ plots of the atomic configurations. These methods consistently testify to the stability of the trans (fully extended) character of the strain-free alkyl chains up to room temperature. The chains retain much of this conformation even when the layers are compressed by the application of pressure, to which the chains respond by ‘folding’ at the ends attaching them to the substrate planes while maintaining directions which are mainly normal to these planes. A non-zero gap between the layers is also maintained. A pressure of about 50 kbar abruptly causes all motion in the chains to cease, resulting in a highly ordered lattice structure.
CATLOW, CRA, CORISH, J., HENNESSY, J. and MACKRODT, WC (1988), Atomistic Simulation of Defect Str... more CATLOW, CRA, CORISH, J., HENNESSY, J. and MACKRODT, WC (1988), Atomistic Simulation of Defect Structures and Ion Transport in α-Fe 2 O 3 and α-Cr 2 O 3. Journal of the American Ceramic Society, 71: 42–49. doi: 10.1111/j. 1151-2916.1988. tb05758. x
Dedicated to Dr. rer. nat. habil. J. TELTOW on the occasion of his 70th birthday Thermal depolari... more Dedicated to Dr. rer. nat. habil. J. TELTOW on the occasion of his 70th birthday Thermal depolarization for single crystals of silver bromide doped with cadmium is measured using improved data acquisition techniques. Two overlapping dipole reorientation peaks a t 92.6 and 99.5 K are analyzed by non-linear least-squares fitting and the rela.xation processes are found to have activation energies of 0.250 and 0.311 eV, respectively. The dependence of the dipole relaxation spectrum on the anneal temperature of the crystal is also investigated systematically and it is concluded that the lower temperature peak is due to nearest-neighbour cadmium-vacancy pairs. This conclusion is also based on theoretical calculations made using the lattice simulation met.hods in the HADES programme of the binding energies of such complexes and on the results of detailed analyses of ionic conductance data measured on the same crystal. The higher tcrnperature peak is thought to be due to the relaxation of a larger complex. Mit einer verbesserten Datenverarbeitungstechnik wird die thermische Depolarisation von mit Kadmium dotierten Silberbromid-Einkristallen gemessen. Zwei uberlappende Dipol-Reorientierungsmaxima bei 92,6 und 99,5 K werden mittels nichtlinearer Anpassung nach der RIethode kleinster Quadrate analysiert und es wird gefunden, daI3 die Relaxationsprozesse dktivierungsenergien von 0,250 bzw. 0,311 eV besitzen. Die Abhangigkeit des Dipol-Relaxationsspektrums von der Temperungstemperatur des Kristalls wird ebenfalls systematisch untersucht und es wird angenommen, daB das Maximum bei der tieferen Temperat.ur durch nachstbenachbarte Kadmium-Leerstellenpaare hervorgerufen wird. Dieser SchluB beruht auch auf mit der Gittersimulationsmethode im HADES-Programm durchgefiihrten theoretischen Berechnungen der Bindungsenergien solcher Komplexe und auf den Ergebnissen ausfiihrlicher Analysen der Ionenleitfahigkeit, die an demselben Kristall gemessen wird. Es wird angenommen, daB das Maximum bei der hoheren Temperatur durch die Relaxation eines groljeren Komplexes hervorgerufen wird.
... 56 MJ Clancy et al. / International Journal of Pharmaceutics 105 (1994) 47-56 mechanistic ana... more ... 56 MJ Clancy et al. / International Journal of Pharmaceutics 105 (1994) 47-56 mechanistic analysis and application to poiypeptide deliv-ery. J. Pharm. Sei.. 78 (1989) 370-375. Tyle, P. and Agrawala, P., Drug delivery by phonophoresis. Pharm. Res.. 6 (1989) 355-361. Walker, M ...
The role of defects in matter transport through solid materials is discussed and the nature of th... more The role of defects in matter transport through solid materials is discussed and the nature of the principal types of point and extended defects, as well as the evidence for their existence, is examined. The equations governing the participation of defects in ionic conduction and diffusion are developed from first principles as is the relationship between these processes. The experimental methods available for the measurement of matter transport in solid materials and the techniques used for effective data analyses are described. Finally the current level of knowledge of diffusion processes in a range of different types of solids is reviewed.
It is a truism that the more we learn about anything the more complex that subject becomes. This ... more It is a truism that the more we learn about anything the more complex that subject becomes. This is especially true of our understanding of the exact arrangement of atoms or ions which make up solid materials.The rapid development and improvement of the techniques by which defects solids are detected and characterized, and which form the subject matter of this book, have necessitated constant revision of our concepts of perfect and defective solids. It is, for example, no longer adequate to confine our attention to isolated point defects without also considering their aggregation to form more complex defect centres and eventually even separate phases, their relationship with non-stoichiometry and their interactions with each other and with the linear and planar defects with which they co-exist. Similarly, the precise structural information now available for many materials reveals that non-stoichiometric phases may exist as modulated structures in which the composition may vary in a continuous fashion to yield commensurate, semi-commensurate and incommensur-ate structures. The presence of shear planes also changes the composit-ion of non-stoichiometric phases.
The nature and occurrence of fast-ion conduction (FIC) in solids is described and explained and t... more The nature and occurrence of fast-ion conduction (FIC) in solids is described and explained and the materials in which it is operative, ranging from crystals through amorphous glassy electrolytes to ionically conducting polymeric complexes, are classified. FIC processes in a number of materials which are of particularly technological interest e.g. oxygen ion conductors and glassy and polymeric electrolytes, are discussed in detail. A number of key applications of these materials in solid state ionics and, in particular recently reported progress is also described. The emphasis is on the overall physical properties that are required in the design of a successful optimized material
ABSTRACT Apart from man’s innate need to model and the satisfaction that a good model can bring, ... more ABSTRACT Apart from man’s innate need to model and the satisfaction that a good model can bring, the real purpose of scientific modelling is to increase our understanding of a system. More importantly, it provides the basis from which to move forward to understand more complex systems and to design such new systems for specific applications by making predictions about their properties. Simple ionic solids, such as the alkali and silver halides, some fluoritestructured crystals and binary oxides, provide the most accessible and well-developed testing grounds for the study, both experimental and theoretical, of point defects in crystalline materials. This is because defects in these crystals typically carry a charge different from those on the ions that comprise the normal components of the matrix. Their presence, nature, interactions and movements can therefore be rather easily quantitatively determined through the measurement of readily observed macroscopic properties such as ionic conductivity. These charges can be present whether the defects are intrinsic or extrinsic. Intrinsic defects, such as Schottky or Frenkel defects, are equilibrium thermodynamic defects and exist in all materials because the balance between the enthalpy required for their formation in a perfect lattice and the resulting increase in the entropy of the system gives rise to a minimum in the Gibbs free energy. There is a corresponding equilibrium intrinsic defect concentration at each temperature.
The thermochromism of poly(3-alkylthiophene)s is explained as a buckling of the main chain by tor... more The thermochromism of poly(3-alkylthiophene)s is explained as a buckling of the main chain by torsions around the interring bonds resulting in a dilation of the rc band energy gap. Atomi>tic simulation calculations show that the necessity to preserve translational periodicity imposes restrictions on the permitted torsions. In our model the effect of heating causes a relative shift of adjacent polymLr chains, changing the ring stacking from 'staggered' to 'eclipsed', in which the chains undergo a spontaneous torsion of 20".
Simulating the \hbox{BF}_{4}^{-} -doped poly(3-octylthiophene) lattice by molecular dynamics resu... more Simulating the \hbox{BF}_{4}^{-} -doped poly(3-octylthiophene) lattice by molecular dynamics results in a structure in which dopant ions intercalate as a sandwich between thiophene rings on adjacent polymer chains. The ions occupy sites in channels parallel to the polymer main chain, which retains a high degree of planarity in contrast to the pristine (undoped) polymer. Even when lattice imperfections are created by expanding the cell, Coulomb forces ensure that the intercalation features containing the dopant channels are largely retained. On applying electric fields in the principal directions of the 'perfect lattice' it is found that the ions migrate most readily along the ion-channel directions (the lattice c axis), leaving the lattice undisturbed. Although higher electric fields cause dopant migration to occur perpendicular to the channel directions they destroy the intercalated lattice. In the reduced-order lattice regions substantial motion of the ions are predicted at a critical value of the lattice parameter.
The high-temperature conductivity of pure AgCl has been reexamined with a view to establishing mo... more The high-temperature conductivity of pure AgCl has been reexamined with a view to establishing more precisely the mobility parameters for non-collinear interstitialcy motion of Ag+ interstitials. The possible roles of direct interstitial jumps, Schottky defects, and temperature dependent activation energies has been assessed. Fomulae are given for the activity coefficients of interstitials and vacancies evaluated to O(x2) in an approximation that uses a sphericalized Brillouin zone and inlcudes only the cycle sum contributions. These activity coefficients are compared with those evaluated from the Debye-Huckel formula and their effect on the defect parameters obtained from conductivity data is assessed. Die Hochtemperaturleitfahigkeit von reinem AgCl wurde im Hinblick auf eine genauere Festlegung der Beweglichkeitsparameter fur nicht-kollineare Zwischengitterbewegung von Ag+-Zwischengitterionen erneut uberpruft. Die mogliche Rolle direkter Zwischengitterspriinge, Schottky-Defekte und temperaturabhangiger Aktivierungsenergien wurde abgeschatzt. Es werden Gleichungen fur die Aktivitatskoeffizienten von Zwischengitterteilchen und Leerstellen angegeben, die bis zu O(xz) ausgewertet werden in einer Naherung, welche spharikalisierte Brillouin-Zonen benutzt und nur die Beitrage der Zyklussummen enthalt. Diese Aktivitatskoeffizienten werden mit den nach der Debye-Huckel-Gleichung ausgewerteten verglichen und ihr EinfluB auf die aus den Leitfahigkeitsdaten erhaltenen Defektparameter wird abgeschatzt.
Abstract The conformations of the chains constituting the hydrophilic component of alkyl monolaye... more Abstract The conformations of the chains constituting the hydrophilic component of alkyl monolayers and bilayers are investigated by performing molecular dynamics atomistic simulations on these systems at different temperatures. Several monitoring techniques are used to reveal the chain conformations, including atom pair radial distribution functions, evolutions of the torsional angles over thousands of timesteps, frequency distributions of the torsionl angles and ‘snapshot’ plots of the atomic configurations. These methods consistently testify to the stability of the trans (fully extended) character of the strain-free alkyl chains up to room temperature. The chains retain much of this conformation even when the layers are compressed by the application of pressure, to which the chains respond by ‘folding’ at the ends attaching them to the substrate planes while maintaining directions which are mainly normal to these planes. A non-zero gap between the layers is also maintained. A pressure of about 50 kbar abruptly causes all motion in the chains to cease, resulting in a highly ordered lattice structure.
CATLOW, CRA, CORISH, J., HENNESSY, J. and MACKRODT, WC (1988), Atomistic Simulation of Defect Str... more CATLOW, CRA, CORISH, J., HENNESSY, J. and MACKRODT, WC (1988), Atomistic Simulation of Defect Structures and Ion Transport in α-Fe 2 O 3 and α-Cr 2 O 3. Journal of the American Ceramic Society, 71: 42–49. doi: 10.1111/j. 1151-2916.1988. tb05758. x
Dedicated to Dr. rer. nat. habil. J. TELTOW on the occasion of his 70th birthday Thermal depolari... more Dedicated to Dr. rer. nat. habil. J. TELTOW on the occasion of his 70th birthday Thermal depolarization for single crystals of silver bromide doped with cadmium is measured using improved data acquisition techniques. Two overlapping dipole reorientation peaks a t 92.6 and 99.5 K are analyzed by non-linear least-squares fitting and the rela.xation processes are found to have activation energies of 0.250 and 0.311 eV, respectively. The dependence of the dipole relaxation spectrum on the anneal temperature of the crystal is also investigated systematically and it is concluded that the lower temperature peak is due to nearest-neighbour cadmium-vacancy pairs. This conclusion is also based on theoretical calculations made using the lattice simulation met.hods in the HADES programme of the binding energies of such complexes and on the results of detailed analyses of ionic conductance data measured on the same crystal. The higher tcrnperature peak is thought to be due to the relaxation of a larger complex. Mit einer verbesserten Datenverarbeitungstechnik wird die thermische Depolarisation von mit Kadmium dotierten Silberbromid-Einkristallen gemessen. Zwei uberlappende Dipol-Reorientierungsmaxima bei 92,6 und 99,5 K werden mittels nichtlinearer Anpassung nach der RIethode kleinster Quadrate analysiert und es wird gefunden, daI3 die Relaxationsprozesse dktivierungsenergien von 0,250 bzw. 0,311 eV besitzen. Die Abhangigkeit des Dipol-Relaxationsspektrums von der Temperungstemperatur des Kristalls wird ebenfalls systematisch untersucht und es wird angenommen, daB das Maximum bei der tieferen Temperat.ur durch nachstbenachbarte Kadmium-Leerstellenpaare hervorgerufen wird. Dieser SchluB beruht auch auf mit der Gittersimulationsmethode im HADES-Programm durchgefiihrten theoretischen Berechnungen der Bindungsenergien solcher Komplexe und auf den Ergebnissen ausfiihrlicher Analysen der Ionenleitfahigkeit, die an demselben Kristall gemessen wird. Es wird angenommen, daB das Maximum bei der hoheren Temperatur durch die Relaxation eines groljeren Komplexes hervorgerufen wird.
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Papers by J. Corish