Atomistic Simulations of the (1014) Surface of Carbonate Minerals

2000 ◽  
Vol 620 ◽  
Author(s):  
Kate Wright ◽  
Randall T. Cygan ◽  
Ben Slater
Keyword(s):  
Atomistic Simulation ◽  
Atomistic Simulations ◽  
Simulation Methods ◽  
Carbonate Group ◽  
Surface Energies ◽  
Influence Of Water ◽  
Dry And Wet Conditions ◽  
Potential Parameters ◽  
Water Species ◽  
Monolayer Coverage

ABSTRACTAtomistic simulation methods have been used to model the structure of the (1014) surfaces of calcite, dolomite, and magnesite under dry and wet conditions. The potential parameters for the carbonate and water species contain shell terms to model the polarizability of the oxygen atoms. These static calculations show that the surfaces undergo relaxation leading to the rotation and distortion of the carbonate groups with associated movement of cations. The dry surface energies are 0.322, 0.247, and 0.256 Jm−2 for calcite, dolomite, and magnesite respectively. The influence of water on the surface structure and energies has been investigated for monolayer coverage. When fully hydrated with a monolayer of water, the surface energy for calcite is reduced indicating a stabilization of the surface with hydration. The extent of carbonate group distortion is greater for the dry surfaces compared to the hydrated surfaces, and for the dry calcite relative to that for dry magnesite.

Theoretical Chemical Characterization of Energetic Materials

2005 ◽  
Vol 896 ◽  
Author(s):  
Betsy Mavity Rice ◽  
Edward F. C. Byrd
Keyword(s):  
Energetic Materials ◽  
Atomistic Simulation ◽  
State Of The Art ◽  
Energetic Material ◽  
Chemical Characterization ◽  
Theoretical Chemistry ◽  
Atomistic Simulations ◽  
Simulation Methods ◽  
Design Development

AbstractOur research is focused on developing computational capabilities for the prediction of properties of energetic materials associated with performance and sensitivity. Additionally, we want to identify and characterize the dynamic processes that influence conversion of an energetic material to products upon initiation. We are attempting to achieve these goals through the use of standard atomistic simulation methods. In this paper various theoretical chemistry methods and applications to energetic materials will be described. Current capabilities in predicting structures, thermodynamic properties, and dynamic behavior of these materials will be demonstrated. These are presented to exemplify how information generated from atomistic simulations can be used in the design, development, and testing of new energetic materials. In addition to illustrating current capabilities, we will discuss limitations of the methodologies and needs for advancing the state of the art in this area.

scholarly journals Atomistic simulation of CeO2 surface hydroxylation: implications for glass polishing

2008 ◽  
Vol 43 (12) ◽  
pp. 4157-4162 ◽  
Author(s):  
Christopher R. Stanek ◽  
Averyl H. H. Tan ◽  
Scott L. Owens ◽  
Robin W. Grimes
Keyword(s):  
Atomistic Simulation ◽  
Morphological Changes ◽  
Dissociative Adsorption ◽  
Atomistic Simulations ◽  
Surface Energies ◽  
Simulation Techniques ◽  
Surface Configuration ◽  
Adsorption Of Water ◽  
Surface Hydroxylation ◽  
Glass Polishing

AbstractAtomistic simulation techniques have been used to investigate the dissociative adsorption of water on the (110), (111), and (100) low index surfaces of CeO2, as well as a so-called “trench” surface configuration. Several different coverages of water have been considered to better understand how the hydroxylation process progresses. Hydroxylation energies and surface energies of CeO2 calculated via atomistic simulations are compared to similar results for other fluorite oxides. Finally, the modification of CeO2 crystallite morphology in the presence of water is predicted from the changes in surface energy and the implications of these morphological changes for glass polishing are discussed.

Theoretical chemical characterization of energetic materials

2006 ◽  
Vol 21 (10) ◽  
pp. 2444-2452 ◽  
Author(s):  
Betsy M. Rice ◽  
Edward F.C. Byrd
Keyword(s):  
Energetic Materials ◽  
Atomistic Simulation ◽  
State Of The Art ◽  
Energetic Material ◽  
Chemical Characterization ◽  
Theoretical Chemistry ◽  
Atomistic Simulations ◽  
Simulation Methods ◽  
Design Development

Our research is focused on developing computational capabilities for the prediction of properties of energetic materials associated with performance and sensitivity. Additionally, we want to identify and characterize the dynamic processes that influence conversion of an energetic material to products upon initiation. We are attempting to achieve these goals through the use of standard atomistic simulation methods. In this paper, various theoretical chemistry methods and applications to energetic materials will be described. Current capabilities in predicting structures, thermodynamic properties, and dynamic behavior of these materials will be demonstrated. These are presented to exemplify how information generated from atomistic simulations can be used in the design, development, and testing of new energetic materials. In addition to illustrating current capabilities, we will discuss limitations of the methodologies and needs for advancing the state of the art in this area.

Critical Evaluation of Atomistic Simulations of 3D Dislocation Configurations

1995 ◽  
Vol 408 ◽  
Author(s):  
Vijay B. Shenoy ◽  
Rob Phillips
Keyword(s):  
Atomistic Simulation ◽  
Critical Evaluation ◽  
Line Tension ◽  
Peierls Stress ◽  
Atomistic Simulations ◽  
Lattice Resistance ◽  
New Challenges ◽  
Fixed Boundaries ◽  
Important Objective ◽  
Approximate Scheme

AbstractThough atomistic simulation of 3D dislocation configurations is an important objective for the analysis of problems ranging from point defect condensation to the operation of Frank-Read sources such calculations pose new challenges. In particular, use of finite sized simulation cells produce additional stresses due to the presence of fixed boundaries in the far field which can contaminate the interpretation of these simulations. This paper discusses an approximate scheme for accounting for such boundary stresses, and is illustrated via consideration of the lattice resistance encountered by straight dislocations and simulations of 3D bow out of pinned dislocation segments. These results allow for a reevaluation of the concepts of the Peierls stress and the line tension from the atomistic perspective.

Length Scale Effects in Materials Deformation of Nano and Microscale Au Structures

2009 ◽  
Author(s):  
Jie Lian ◽  
Junlan Wang
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Size Effect ◽  
Sample Size ◽  
Atomistic Simulation ◽  
Scale Effects ◽  
Elastic Recovery ◽  
Boundary Effect ◽  
Dislocation Nucleation ◽  
Atomistic Simulations

In this study, intrinsic size effect — strong size dependence of mechanical properties — in materials deformation was investigated by performing atomistic simulation of compression on Au (114) pyramids. Sample boundary effect — inaccurate measurement of mechanical properties when sample size is comparable to the indent size — in nanoindentation was also investigated by performing experiments and atomistic simulations of nanoindentation into nano- and micro-scale Au pillars and bulk Au (001) surfaces. For intrinsic size effect, dislocation nucleation and motions that contribute to size effect were analyzed for studying the materials deformation mechanisms. For sample boundary effect, in both experiments and atomistic simulation, the elastic modulus decreases with increasing indent size over sample size ratio. Significantly different dislocation motions contribute to the lower value of the elastic modulus measured in the pillar indentation. The presence of the free surface would allow the dislocations to annihilate, causing a higher elastic recovery during the unloading of pillar indentation.

Synergistic effect of supercritical CO2 and organic solvent on exfoliation of graphene: experiment and atomistic simulation studies

2019 ◽  
Vol 21 (39) ◽  
pp. 22149-22157 ◽  
Author(s):  
Lixi Liu ◽  
Yan Chen ◽  
Fei Dang ◽  
Yilun Liu ◽  
Xiaogeng Tian ◽  
...  
Keyword(s):  
Synergistic Effect ◽  
Organic Solvent ◽  
Supercritical Co2 ◽  
Atomistic Simulation ◽  
Atomistic Simulations ◽  
Simulation Studies

The synergistic effect of scCO2 and organic solvent on exfoliation of graphene was studied by experiments and atomistic simulations.

Critical Evaluation of Atomistic Simulations of 3D Dislocation Configurations

1995 ◽  
Vol 409 ◽  
Author(s):  
Vijay B. Shenoy ◽  
Rob Phillips
Keyword(s):  
Atomistic Simulation ◽  
Critical Evaluation ◽  
Line Tension ◽  
Peierls Stress ◽  
Atomistic Simulations ◽  
Lattice Resistance ◽  
New Challenges ◽  
Fixed Boundaries ◽  
Important Objective ◽  
Approximate Scheme

AbstractThough atomistic simulation of 3D dislocation configurations is an important objective for the analysis of problems ranging from point defect condensation to the operation of Frank-Read sources such calculations pose new challenges. In particular, use of finite sized simulation cells produce additional stresses due to the presence of fixed boundaries in the far field which can contaminate the interpretation of these simulations. This paper discusses an approximate scheme for accounting for such boundary stresses, and is illustrated via consideration of the lattice resistance encountered by straight dislocations and simulations of 3D bow out of pinned dislocation segments. These results allow for a reevaluation of the concepts of the Peierls stress and the line tension from the atomistic perspective.

Stucture of 1/2 Dislocations In γ-Tial by High Resolution Tem and Embedded Atom Method Modelling

1994 ◽  
Vol 364 ◽  
Author(s):  
J. P. Simmons ◽  
M. J. Mills ◽  
S. I. Rao
Keyword(s):  
High Resolution ◽  
Atomistic Simulation ◽  
Embedded Atom Method ◽  
Simulation Methods ◽  
Embedded Atom ◽  
A Value ◽  
High Resolution Tem ◽  
Atomistic Calculations ◽  
Range Of Values ◽  
Limit Estimate

AbstractHigh Resolution TEM (HRTEM) observations of a dislocation in γ-TiAl are compared directly with atomistic calculations of dislocation structures performed with atomistic potentials in order to obtain an estimate of the Complex Stacking Fault Energy (γcsf). A value of between 470 and 620 mJ/M2 was obtained. HRTEM observations are presented of a Ti-52AI sample, containing a dislocation with Burgers vector 1/2<110> and 60° line orientation. This image is matched against images simulated from the outputs of Embedded Atom Method (EAM) simulations, using potentials that were fit to bulk γ-TiAl properties. Two atomistic simulation methods were employed in order to give the range of values for γcsf. In the first of these methods, three EAM potentials were used to simulate the stress-free core structure. These were fit so as to produce three different values of γcsf, all other properties being roughly the same as the literature values for γ-TiAI. All of these potentials produced cores that were more extended than the experimental observation. Thus a value of 470 mJ/M2, being the highest value of γcsf obtainable for the EAM potentials, is reported as a low limit estimate of γcsf for γ-TiAl. An upper limit estimate of the value of γcsf was obtained by applying an external ‘Escaig’ stress that forced the Shockley partials to further constrict, simulating the effect of an increase in γcsf, The preliminary value calculated from this procedure was 620 mJ/M2.

Atomistic Simulation of ½ Screw Dislocations in BCC Tungsten

2008 ◽  
Vol 59 ◽  
pp. 247-252 ◽  
Author(s):  
Jan Fikar ◽  
Robin Schäublin ◽  
Carolina Björkas
Keyword(s):  
Screw Dislocation ◽  
Atomistic Simulation ◽  
Bond Order ◽  
Analytical Approach ◽  
Atomistic Simulations ◽  
Screw Dislocations ◽  
Atom Model ◽  
Embedded Atom ◽  
Bond Order Potential

Atomistic simulations are used to describe the ½<111> screw dislocation in tungsten. Two different embedded atom model (EAM) potentials and one bond-order potential (BOP) are compared. A new analytical approach for constructing asymmetrical screw dislocations is presented.

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