Papers by Geoffrey David Price
Computer simulation of the structure, lattice dynamics, and thermodynamics of ilmenite-type MgSiO3
American Mineralogist, Apr 1, 1988
Frontiers in sustainability, Jul 29, 2021
In leadership positions at UCL, we have spent more than a decade seeking to fulfil our university... more In leadership positions at UCL, we have spent more than a decade seeking to fulfil our university's founding commitment-inspired almost two centuries ago by the utilitarian philosopher Jeremy Bentham-to innovation, accessibility, and relevance for the benefit of humanity. Our guiding principle has been to make our institution and its activities greater than the sum of its parts. To enable us to have most impact in "sustainable human progress," we have focused our approach on cross-disciplinarity-by which we mean collaboration between experts in different disciplines that transcends subject boundaries-because the problems faced by society cannot be solved by research from one discipline alone. In recent years we have come to understand the boundaries between disciplines to be a subset of the many types of barriers-such as those between communities (disciplinary, academic and otherwise) and between different kinds of activity-that can inhibit the fulfilment of our vision to maximise our public benefit. In order to address crucial challenges-from the local to the global-we need to form collaborations across society that increase our mutual knowledge and engagement. We need to understand how the translation and application of knowledge will change in different settings and according to different practicalities. And we need to better reflect and enhance our role as convenors of different stakeholders to promote greater shared dialogue, co-creation and action.
The Stability of Minerals
Springer eBooks, 1993
Preface. The stability of minerals: an introduction - N L Ross and G D Price Bond topology, bond ... more Preface. The stability of minerals: an introduction - N L Ross and G D Price Bond topology, bond valence and structure stability - F C Hawthorne Electronic paradoxes in the structures of minerals - J K Burdett Lattice vibration and mineral stability - N L Ross Thermodynamics of phase transitions in minerals: a macroscopic approach - M A Carpenter The stability of modulated structures - J D C McConnell Thermochemistry of tetrahedrite-tennanite fahlores - R O Sack Thermodynamic data for minerals: a critical assessment - M Engi The stability of clays - B Velde
The factors influencing solid state structure — A modern Mendeleyevian answer
Solid State Communications, Dec 1, 1981
ABSTRACT
Chemischer Informationsdienst, Apr 13, 1982
Physical review, Sep 15, 1981
AB2 octets and double octets, and AB2X4 spinels. With the use of r+/r, the crystal ionic radii, t... more AB2 octets and double octets, and AB2X4 spinels. With the use of r+/r, the crystal ionic radii, the sorting is tolerable only if the usual restrictions. of the mechanical model (radius ratio rules) are relaxed. R /R are poor indices for AB2 and AB2X4, but r"/r and P"/P are excellent for all three systems. It is suggested that the traditional packing ideas based on size (and viewed semiquantitatively here using the r~) are directly related to modern charge-control aspects (via electronegativity differences) of molecular structures, and both cari be viewed as very important factors in determining structural preference.
ObituaryMarcelle K. Boudagher-Fadel, B.Sc., M.Sc., Ph.D. 1956-2022
Journal of Foraminiferal Research, Oct 1, 2022
Computer Modelling of the Structure and Thermodynamic Properties of Silicate Minerals
Springer eBooks, 1990
One of the major aims of mineralogical research is to determine which minerals exist under given ... more One of the major aims of mineralogical research is to determine which minerals exist under given pressure, temperature and compositional conditions. This is of particular importance as mass transport deep in the Earth’s Mantle, and ultimately plate motion, will be governed by the behaviour of the component minerals. Hence a detailed understanding of their thermodynamic and kinetic properties under extreme pressures and temperatures will aid in our understanding of Mantle dynamics. Much of our current knowledge of the composition and properties of the Mantle comes from seismic studies, which show that the Earth has a layered structure. For example the Mantle is divided into three distinct layers, with the Upper Mantle comprising principally of olivine-structured magnesium silicate (forsterite), the Transition Zone of the same composition but comprised of minerals with the spinel structure, and finally another magnesium silicate mineral which is believed to have the perovskite structure forms the bulk of the Lower Mantle. These assignments are not unambiguous however but recent work using X-ray diffraction techniques with high pressure diamond anvil cells [1] is making progress in elucidating the crystal structure and relative stability of these phases under realistic conditions. As these experimental studies are often difficult, an attractive alternative is the use of computer simulation methods, which can now be used to model both the pressures and temperatures existing in the Mantle. Two recent developments in the field of atomistic simulation have made it possible to model silicate minerals under Mantle conditions.
Gravity glide and plate tectonics
Geological Society, London, Special Publications, 1988
Abstract We briefly discuss the three groups of mechanisms which are generally held to be respons... more Abstract We briefly discuss the three groups of mechanisms which are generally held to be responsible for plate motions, namely basal traction, slab pull, and ridge push. We conclude that individually, or in combination, these mechanisms are insufficient to account for known plate behaviour. Instead, we reintroduce and expand upon an idea proposed by Hales (1969) that the driving force for plate motion is the body weight of the lithosphere, which gives rise to gravity glide on the inclined interface between the lithosphere and asthenosphere. It is shown that this mechanism is capable of producing an average horizontal stress of as much as 6 kbar and is able to explain (1) continental splitting, (2) the initiation of subduction, and (3) observable plate motions, as well as a variety of effects requiring high lateral stresses. This is the first model to be proposed that successfully provides a quantitatively and physically viable mechanism to explain plate-tectonic processes and the behaviour of the Earth’s lithosphere.
Defects and diffusion in MgSiO3perovskite: a computer simulation
Geophysical monograph, Mar 18, 2013
Thermoelastic properties of magnesiow
Defects and diffusion in MgSiO3 perovskite: A computer simulation
Geophysical Monograph Series, 2013
Computer modelling of B2O3. II. Molecular dynamics simulations of vitreous structures
Journal of Physics: Condensed Matter, 1995
ABSTRACT We use our recently developed interatomic potential, which can reproduce the crystal str... more ABSTRACT We use our recently developed interatomic potential, which can reproduce the crystal structures of both phases of B2O3, in a molecular dynamics study of the structures of vitreous B2O3. Our calculated results suggest that the use of a partial charge model, and the inclusion of a B-O-B bond-bending, three-body term are important in reproducing the structure of this vitreous material. They also demonstrate the presence of boroxol (six-membered) rings in the simulated structures. Improved results are obtained when the potentials are refined by the inclusion of coordination-dependent terms which result in a higher proportion of boroxol rings in accordance with experimental data.
A high-pressure study of ∊-FeSi, between 0 and 8.5 GPa, by time-of-flight neutron powder diffraction
Journal of Applied Crystallography, 1996
ABSTRACT
Electron Microscopy of Shock-Produced Polymorphs of Olivine and Pyroxene in the Tenham Chondrite
The structure of high pressure carbonate glasses: Implications for carbonatite melts
High Pressure Research, 1991
ABSTRACT
Evidence for kinetic effects on shock wave metamorphism- Laboratory experiments compared with inferences from studies of natural impact craters
ABSTRACT Laboratory calibrations of shock metamorphism are in substantial disagreement with infer... more ABSTRACT Laboratory calibrations of shock metamorphism are in substantial disagreement with inferences from studies of material in natural large impact craters. This disagreement is interpreted as evidence for kinetic effects.
High Pressure Elastic Anisotropy of α -PbO2-Type SiO2
ABSTRACT
Physics and Chemistry of Minerals, 2008
We have used density functional theory to investigate the stability of MgAl 2 O 4 polymorphs unde... more We have used density functional theory to investigate the stability of MgAl 2 O 4 polymorphs under pressure. Our results can reasonably explain the transition sequence of MgAl 2 O 4 polymorphs observed in previous experiments. The spinel phase (stable at ambient conditions) dissociates into periclase and corundum at 14 GPa. With increasing pressure, a phase change from the two oxides to a calcium-ferrite phase occurs, and finally transforms to a calcium-titanate phase at 68 GPa. The calcium-titanate phase is stable up to at least 150 GPa, and we did not observe a stability field for a hexagonal phase or periclase + Rh 2 O 3 (II)-type Al 2 O 3. The bulk moduli of the phases calculated in this study are in good agreement with those measured in high-pressure experiments. Our results differ from those of a previous study using similar methods. We attribute this inconsistency to an incomplete optimization of a cell shape and ionic positions at high pressures in the previous calculations.
Structural phase transitions in IrO2at high pressures
Journal of Physics: Condensed Matter, 2008
ABSTRACT
Uploads
Papers by Geoffrey David Price