Lattice Dynamics from Force-Fields as a Technique for Mineral Physics

Gale, Julian D.; Wright, Kate

doi:10.2138/rmg.2010.71.18

Cited by 9 publications

(9 citation statements)

References 78 publications

(89 reference statements)

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“…Quantum mechanical models allow probing of the physics of geomaterials at extreme geological conditions such as the conditions of temperatures well in excess of 3000 C and pressures in excess of 130 GPa pressure found deep in the earth. 3 The technique is ideally suited for supercomputer implementations as molecular dynamics has a long track record of at least 50 years in the area of condensed matter physics. In earth sciences the current status of these calculations is mainly limited to applications in mineralogy and nanochemistry, and the approach has not yet bridged the scales from thousands of atoms to describing the behaviour of larger rock specimens consisting of mineral aggregates.…”

Section: Microstructure Modelling Of Earth Materialsmentioning

confidence: 99%

Multiscale coupling and multiphysics approaches in earth sciences: Applications

Regenauer‐Lieb¹,

Veveakis²,

Poulet³

et al. 2013

j coupled syst multiscale dyn

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Geoscientists are confronted with the challenge of assessing nonlinear phenomena that result from multiphysics coupling across multiple scales from the quantum level to the scale of the earth and from femtosecond to the 4.5 Ga of history of our planet. We neglect in this review electromagnetic modelling of the processes in the Earth's core, and focus on four types of couplings that underpin fundamental instabilities in the Earth. These are thermal (T), hydraulic (H), mechanical (M) and chemical (C) processes which are driven and controlled by the transfer of heat to the Earth's surface. Instabilities appear as faults, folds, compaction bands, shear/fault zones, plate boundaries and convective patterns. Convective patterns emerge from buoyancy overcoming viscous drag at a critical Rayleigh number. All other processes emerge from non-conservative thermodynamic forces with a critical critical dissipative source term, which can be characterised by the modified Gruntfest number Gr. These dissipative processes reach a quasi-steady state when, at maximum dissipation, THMC diffusion (Fourier, Darcy, Biot, Fick) balance the source term. The emerging steady state dissipative patterns are defined by the respective diffusion length scales. These length scales provide a fundamental thermodynamic yardstick for measuring instabilities in the Earth. The implementation of a fully coupled THMC multiscale theoretical framework into an applied workflow is still in its early stages. This is largely owing to the four fundamentally different lengths of the THMC diffusion yardsticks spanning micro-metre to tens of kilometres compounded by the additional necessity to consider microstructure information in the formulation of enriched continua for THMC feedback simulations (i.e., micro-structure enriched continuum formulation). Another challenge is to consider the important factor time which implies that the geomaterial often is very far away from initial yield and flowing on a time scale that cannot be accessed in the laboratory. This leads to the requirement of adopting a thermodynamic framework in conjunction with flow theories of plasticity. This framework allows, unlike consistency plasticity, the description of both solid mechanical and fluid dynamic instabilities. In the applications we show the similarity of THMC feedback patterns across scales such as brittle and ductile folds and faults.

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Section: Microstructure Modelling Of Earth Materialsmentioning

confidence: 99%

Multiscale coupling and multiphysics approaches in earth sciences: Applications

Regenauer‐Lieb¹,

Veveakis²,

Poulet³

et al. 2013

j coupled syst multiscale dyn

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“…Schreckenbach and Shamov [24] have recently discussed the various approximations used in computational chemistry of actinides. Due to the limitations of current functionals, DFT results will quantitatively differ from experimental results [25].…”

Section: Modeling Schemesmentioning

confidence: 93%

“…This limitation makes it difficult to model realistic surfaces and interfaces, which hold the key to ceramic dissolution processes. Gale and Wright [25] have pointed out that despite the ongoing increases in computational power many problems of interest continue to lie beyond the scope of DFT. Therefore, the main value of DFT in the study of ceramic waste forms lies in its ability to provide reliable data to fill gaps where experimental data is not available and to parameterize the next higher scale (coarser model) in the modeling hierarchy.…”

Section: Modeling Schemesmentioning

confidence: 99%

Challenges in Modeling the Degradation of Ceramic Waste Forms

Devanathan¹,

Gao²,

X³

2011

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We identify the state of the art, gaps in current understanding, and key research needs in the area of modeling the long-term degradation of ceramic waste forms for nuclear waste disposition. The directed purpose of this report is to define a roadmap for Waste IPSC needs to extend capabilities of waste degradation to ceramic waste forms, which overlaps with the needs of the subcontinuum scale of FMM (fundamental methods and method) interests. The key knowledge gaps are in the areas of i) methodology for developing reliable interatomic potentials to model the complex atomic-level interactions in waste forms; ii) characterization of water interactions at ceramic surfaces and interfaces; and iii) extension of atomic-level insights to the long time and distance scales relevant to the problem of actinide and fission product immobilization.

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“…17 A major drawback of the BKS model is that the dispersive term coefficients are unphysically large and the partial charges used are too low. 40 By far the most serious shortcoming of BKS is that it leads to both coesite and stishovite being more stable than α-quartzthis can probably be attributed to the large dispersive term in the potential. 22,40 This is contrary to experiment as well as DFT studies (in the generalized gradient approximation) which predict α-quartz to be the most stable polymorph.…”

Section: Introductionmentioning

confidence: 99%

“…40 By far the most serious shortcoming of BKS is that it leads to both coesite and stishovite being more stable than α-quartzthis can probably be attributed to the large dispersive term in the potential. 22,40 This is contrary to experiment as well as DFT studies (in the generalized gradient approximation) which predict α-quartz to be the most stable polymorph. 12 BKS is also known to overestimate the transition pressure for the stishovite I → II transition.…”

Section: Introductionmentioning

confidence: 99%

A molecular dynamics study of ambient and high pressure phases of silica: Structure and enthalpy variation with molar volume

Rajappa

Sringeri

Yashonath

et al. 2014

The Journal of Chemical Physics

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Extensive molecular dynamics studies of 13 different silica polymorphs are reported in the isothermal-isobaric ensemble with the Parrinello-Rahman variable shape simulation cell. The van Beest-Kramer-van Santen (BKS) potential is shown to predict lattice parameters for most phases within 2%-3% accuracy, as well as the relative stabilities of different polymorphs in agreement with experiment. Enthalpies of high-density polymorphs - CaCl2-type, α-PbO2-type, and pyrite-type - for which no experimental data are available as yet, are predicted here. Further, the calculated enthalpies exhibit two distinct regimes as a function of molar volume-for low and medium-density polymorphs, it is almost independent of volume, while for high-pressure phases a steep dependence is seen. A detailed analysis indicates that the increased short-range contributions to enthalpy in the high-density phases arise not only from an increased coordination number of silicon but also shorter Si-O bond lengths. Our results indicate that amorphous phases of silica exhibit better optimization of short-range interactions than crystalline phases at the same density while the magnitude of Coulombic contributions is lower in the amorphous phase.

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Lattice Dynamics from Force-Fields as a Technique for Mineral Physics

Cited by 9 publications

References 78 publications

Multiscale coupling and multiphysics approaches in earth sciences: Applications

Multiscale coupling and multiphysics approaches in earth sciences: Applications

Challenges in Modeling the Degradation of Ceramic Waste Forms

A molecular dynamics study of ambient and high pressure phases of silica: Structure and enthalpy variation with molar volume

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