Pressure Induced Structural Transformations in Nanocluster Assembled Gallium Arsenide

1998 ◽  
Vol 536 ◽  
Author(s):  
S. Kodiyalam ◽  
A. Chatterjee ◽  
I. Ebbsjö ◽  
R. K. Kalia ◽  
H. Kikuchi ◽  
...  
Keyword(s):  
Bond Angle ◽  
Structural Phase ◽  
High Stress ◽  
Distribution Functions ◽  
Structural Phase Transformation ◽  
Spatially Resolved ◽  
Parallel Molecular Dynamics ◽  
Dynamics Simulations ◽  
Pair Distribution Functions ◽  
Single Cluster

AbstractPressure induced structural phase transformation in nanocluster assembled GaAs is studied using parallel molecular dynamics simulations in the isothermal-isobaric ensemble. In this system the spatial stress distribution is found to be inhomogeneous. As a result structural transformation initiates in the high stress regions at the interface between clusters. Structural and dynamical correlations in the nanophase system are characterized by calculating the spatially resolved bond angle and pair distribution functions and phonon density of states and comparing them with those for a single cluster and bulk crystalline and amorphous systems.

scholarly journals Local structure and distortions of mixed methane-carbon dioxide hydrates

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Bernadette R. Cladek ◽  
S. Michelle Everett ◽  
Marshall T. McDonnell ◽  
Matthew G. Tucker ◽  
David J. Keffer ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Exchange Process ◽  
Carbon Dioxide Sequestration ◽  
Distribution Functions ◽  
Atomic Scale ◽  
Mixed Gas ◽  
Pure Compounds ◽  
Dynamics Simulations ◽  
Pair Distribution Functions ◽  
Methane Carbon

AbstractA vast source of methane is found in gas hydrate deposits, which form naturally dispersed throughout ocean sediments and arctic permafrost. Methane may be obtained from hydrates by exchange with hydrocarbon byproduct carbon dioxide. It is imperative for the development of safe methane extraction and carbon dioxide sequestration to understand how methane and carbon dioxide co-occupy the same hydrate structure. Pair distribution functions (PDFs) provide atomic-scale structural insight into intermolecular interactions in methane and carbon dioxide hydrates. We present experimental neutron PDFs of methane, carbon dioxide and mixed methane-carbon dioxide hydrates at 10 K analyzed with complementing classical molecular dynamics simulations and Reverse Monte Carlo fitting. Mixed hydrate, which forms during the exchange process, is more locally disordered than methane or carbon dioxide hydrates. The behavior of mixed gas species cannot be interpolated from properties of pure compounds, and PDF measurements provide important understanding of how the guest composition impacts overall order in the hydrate structure.

Powder X-ray diffraction and Rietveld analysis of La1−xBaxCoO3 (0

2006 ◽  
Vol 21 (4) ◽  
pp. 304-306 ◽  
Author(s):  
Wanju Luo ◽  
Fangwei Wang
Keyword(s):  
Phase Transformation ◽  
Bond Length ◽  
Structural Properties ◽  
Powder Diffraction ◽  
Bond Angle ◽  
Structural Phase ◽  
Rietveld Analysis ◽  
X Ray Diffraction ◽  
Structural Phase Transformation ◽  
X Ray

Detailed structural properties of La1−xBaxCoO3 (LBCO) have been investigated by means of X-ray powder diffraction and Rietveld analysis. A structural phase transformation from R3c to Pm3m at x=0.30–0.35 has been detected based on a comparison between the refinements of R3c and Pm3m. The Co–O bond length of the CoO6 octahedron expanded rapidly with increasing Ba content when x<0.1, and then it leveled off and kept constant at 0.1⩽x⩾0.35, where the Co–O–Co bond angle reaches 180°. The Co–O bond length expansion resumed with increasing Ba content beyond x=0.35.

A Computer Modelling Study of the Structure of a-C:H

1992 ◽  
Vol 270 ◽  
Author(s):  
D.W. Huxley ◽  
R.J. Newport ◽  
A.N. North ◽  
J.K. Walters
Keyword(s):  
Exploratory Study ◽  
Model Building ◽  
Computer Modelling ◽  
Bond Angle ◽  
Distribution Functions ◽  
Model Structure ◽  
Reverse Monte Carlo ◽  
X Ray ◽  
Pair Distribution Functions ◽  
Carbon Network

ABSTRACTNeutron diffraction data has been used as input to a computer-modelling algorithm based on the “Reverse Monte Carlo” technique. Using this method the positions of ∼ 5000 “atoms” in a box, with full periodicity, are altered until the associated model structure factor agrees with the analogous experimental curve to within errors. It is then possible to estimate the partial pair distribution functions (i.e. those associated with C-C, C-H and H-H correlations), bond angle distributions, coordination number distributions, etc. Whilst X-ray data is well-conditioned for the study of the carbon-carbon network, neutrons are sensitive to the interference terms involving hydrogen. We present an exploratory study of the effectiveness of the RMC method in this context, and suggest viable options for the future use of the method in model building.

Structure and Properties of the GeAsS Glasses from Ab initio Calculations

2014 ◽  
Vol 1035 ◽  
pp. 502-507
Author(s):  
Li An Chen
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Ab Initio ◽  
Bond Angle ◽  
Distribution Functions ◽  
Dynamics Simulation ◽  
Angle Distribution ◽  
Structure And Properties ◽  
Bond Angle Distribution ◽  
Pair Distribution Functions

The structure and properties of the GexAsxS100-2x have been studied by ab initio molecular dynamics simulation. By calculating the pair distribution functions, bond angle distribution functions, we analyze the structure and properties of the alloys. Calculations show that Ge and As are all well combined with S atoms. When x is smaller than 25.0 the binding increases with x , when x is larger than 25.0 the binding decreases with increasing x . The intervention of As atom does not affect the GeS2 formation in Ge40As40S80

Molecular Dynamics Simulations of Thin Film Diamond Growth

1991 ◽  
Vol 223 ◽  
Author(s):  
Bernard A. Pailthorpe ◽  
Peter Knight
Keyword(s):  
Molecular Dynamics ◽  
High Stress ◽  
Distribution Functions ◽  
Film Stress ◽  
Diamond Growth ◽  
Vacuum Arc ◽  
Hartree Fock ◽  
Intermediate Energies ◽  
Dynamics Simulations ◽  
Weber Potential

ABSTRACTThe growth of synthetic diamond thin films is studied by molecular dynamics computer simulations of low energy carbon atom deposition onto a low temperature diamond (111) surface. A previously reported Stillinger Weber potential, reparameterised for sp3 bonding in carbon using Hartree-Fock calculations for small carbon clusters, is used to model the interatomic interactions. The penetration of 1-100eV neutral carbon atoms into a (111) surface of carbon at 100K and the resultant surface atom rearrangements and induced film stress are studied. For intermediate energies (20-60eV) the incident atoms penetrate beneath the exposed (111) surface and increase the lateral compressive stress in the diamond film. It is suggested that diamond films grow from below the exposed surface in a region of locally high stress and tetrahedral coordination. The predicted radial distribution functions agree reasonably with electron diffraction studies of vacuum arc deposited amorphous diamond.

Simulating Structural Transformation of a Cu1553 Nanoparticle on Heating at Atomic Scale

2015 ◽  
Vol 817 ◽  
pp. 736-739
Author(s):  
Jing Zhang ◽  
Peng Yu
Keyword(s):  
Structural Transformation ◽  
Structural Changes ◽  
Distribution Functions ◽  
Atomic Scale ◽  
Embedded Atom Method ◽  
Embedded Atom ◽  
Different Temperatures ◽  
Dynamics Simulations ◽  
Pair Distribution Functions ◽  
Pair Analysis

By means of molecular dynamics simulations within the framework of embedded atom method, we observe the structural transformation of a Cu nanoparticle containing 1553 atoms at atomic scale on a heating series from 350K to 1200K at an increment of 50K. With increasing the temperature, the structural changes result in apparent increases in internal energy. Pair distribution functions (PDFs) and pair analysis (PA) technique as well as the atom packing at different temperatures are used to identify the local structural patterns during the melting of this particle.

Molecular dynamics simulations of EPON-862/DETDA epoxy networks: structure, topology, elastic constants, and local dynamics

Soft Matter ◽  
2019 ◽  
Vol 15 (4) ◽  
pp. 721-733 ◽  
Author(s):  
Spyros V. Kallivokas ◽  
Aristotelis P. Sgouros ◽  
Doros N. Theodorou
Keyword(s):  
Molecular Dynamics ◽  
Elastic Constants ◽  
Distribution Functions ◽  
Glass Temperature ◽  
Segmental Dynamics ◽  
Structure Topology ◽  
Xrd Patterns ◽  
Dynamics Simulations ◽  
Networks Structure ◽  
Pair Distribution Functions

Partial pair distribution functions, XRD patterns, segmental dynamics, elastic constants and glass temperature in EPON862/DETDA epoxy predicted through molecular dynamics.

Structure, Fragmentation, and Phonons in Silicon Microclusters

1992 ◽  
Vol 293 ◽  
Author(s):  
Wei Li ◽  
Rajiv K. Kalia ◽  
Priya Vashishta
Keyword(s):  
Molecular Dynamics ◽  
Structural Information ◽  
Magic Number ◽  
Distribution Functions ◽  
Dynamics Simulation ◽  
Silicon Clusters ◽  
Atom Clusters ◽  
Densities Of States ◽  
Dynamics Simulations ◽  
Pair Distribution Functions

AbstractMolecular-dynamics simulations are performed to investigate structures, vibrational spectra, and fragmentation channels of silicon microclusters ranging in size from 32 to 52 atoms. Structural information is derived from pair-distribution functions, bond-angle distributions, and the structure and statistics of rings. Molecular-dynamics simulation results for energetics suggest that 33, 39, 45 and 51 atom clusters are highly stable. These magic-number clusters have predominantly five and six membered rings. With an increase in “temperature”, most clusters tend to fragment by loosing one atom at a time. Vibrational densities of states of 32-52 atom silicon clusters show only minor deviations from the bulk behavior.

AB INITIO MOLECULAR DYNAMICS STUDY OF DISSOLVED SiO2 IN SUPERCRITICAL WATER

2007 ◽  
Vol 06 (01) ◽  
pp. 49-62 ◽  
Author(s):  
N. L. DOLTSINIS ◽  
M. BURCHARD ◽  
W. V. MARESCH ◽  
A. D. BOESE ◽  
T. FOCKENBERG
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Supercritical Water ◽  
Statistical Error ◽  
Distribution Functions ◽  
Time Span ◽  
Ab Initio Molecular Dynamics ◽  
Spontaneous Polymerization ◽  
Dynamics Simulations ◽  
Pair Distribution Functions

Ab initio molecular dynamics simulations of SiO 2 in supercritical water at temperatures of 900 K and 1200 K and a pressure of 1.5 GPa at concentrations of 5 wt% and 16 wt% have been carried out. The different polymeric forms SiO 4 H 4, Si 2 O 7 H 6, and Si 3 O 10 H 8 are found to be energetically similar within the statistical error, suggesting that all three polymeric forms play an important role in solutions at the above conditions. However, neither spontaneous polymerization nor depolymerization has been observed during the 10-ps time span of the simulations. The dynamic and structural properties of the supercritical solutions have been analyzed in terms of diffusion coefficients, vibrational spectra, and radial pair distribution functions.

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