Melting curves of Cu, Pt, Pd and Au under high pressures

2016 ◽  
Vol 30 (05) ◽  
pp. 1650013 ◽  
Author(s):  
Baoling Zhang ◽  
Baowen Wang ◽  
Qingxin Liu
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
High Pressures ◽  
Melting Curve ◽  
Interaction Forces ◽  
Metal Atoms ◽  
Melting Curves ◽  
Simulation Results ◽  
Dynamics Method ◽  
Good Agreement

Melting curves of Cu, Pt, Pd and Au were calculated via the molecular dynamics method in the temperature range of [Formula: see text]1000–5000 K. The simulation results were compared with the recent high pressure experimental data reported by Errandonea, and the obtained melting curves of Cu, Pt and Au were all in good agreement with his results. For Pd, there were some differences between the obtained melting curve and the experimental data and these differences increased with decreasing temperature to about 7 GPa at 2000 K. The effects of the interaction forces between metal atoms at high atomic densities on the pressure of the system were analyzed. It was found that the pressure in metals predominantly depends on the interaction forces between atoms at high atomic densities. In addition, expressions for melting pressure as a function of temperature have been obtained by fitting the simulation results.

THE CORRELATION BETWEEN BOND ANGLE DISTRIBUTION AND THE COORDINATION OF SILICA LIQUID UNDER PRESSURE

2012 ◽  
Vol 26 (20) ◽  
pp. 1250117 ◽  
Author(s):  
L. T. VINH ◽  
N. V. HUY ◽  
P. K. HUNG
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Bond Angle ◽  
Simple Expression ◽  
Dynamics Simulation ◽  
Angle Distribution ◽  
Bond Angle Distribution ◽  
Simulation Results ◽  
Substantial Change ◽  
Good Agreement

Molecular dynamics simulation is carried out for liquid SiO 2 at pressure ranged from zero to 30 GPa and by using BKS, Born–Mayer type and Morse–Stretch potentials. The constructed models reproduce well the experimental data in terms of mean coordination number, bond angle and pair radial distribution function. Furthermore, the density of all samples can be expressed by a linear function of fractions SiO x. It is found that the topology of units SiO x and linkages OSi y is unchanged upon compression although the liquid undergoes substantial change in its network structure. Consequently, the partial bond angle distribution for SiO x and OSi y is identical for all samples constructed by the same potential. This result allows to establishing a simple expression between total bond angle distribution (BAD) and fraction of SiO x and OSi y. The simulation shows a good agreement between the calculation and simulation results for both total O–Si–O and Si–O–Si BADs. This supports a technique to estimate amount of units SiO x and linkages OSi y on base of total Si–O–Si and O–Si–O BADs measured experimentally.

The penetration and ricochet of ogive-nosed rigid projectiles obliquely impacting metallic targets

2021 ◽  
pp. 204141962110377
Author(s):  
Yaniv Vayig ◽  
Zvi Rosenberg
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Dynamic Pressure ◽  
Oblique Impacts ◽  
Simulation Results ◽  
The Impact ◽  
Penetration Depths ◽  
Resistance To Penetration ◽  
Good Agreement

A large number of 3D numerical simulations were performed in order to follow the trajectory changes of rigid CRH3 ogive-nosed projectiles, impacting semi-infinite metallic targets at various obliquities. These trajectory changes are shown to be related to the threshold ricochet angles of the projectile/target pairs. These threshold angles are the impact obliquities where the projectiles end up moving in a path parallel to the target’s face. They were found to depend on a non-dimensional entity which is equal to the ratio between the target’s resistance to penetration and the dynamic pressure exerted by the projectile upon impact. Good agreement was obtained by comparing simulation results for these trajectory changes with experimental data from several published works. In addition, numerically-based relations were derived for the penetration depths of these ogive-nosed projectiles at oblique impacts, which are shown to agree with the simulation results.

Hydrogen Storage in MgH2 Matrices: An Ab-Initio Study of Mg-MgH2 Interface

2008 ◽  
Vol 139 ◽  
pp. 23-28 ◽  
Author(s):  
Simone Giusepponi ◽  
Massimo Celino ◽  
Fabrizio Cleri ◽  
Amelia Montone
Keyword(s):  
Molecular Dynamics ◽  
Total Energy ◽  
Ab Initio ◽  
Atomic Hydrogen ◽  
Level Structure ◽  
Atomic Level ◽  
Work Of Adhesion ◽  
Ab Initio Study ◽  
Dynamics Method ◽  
Good Agreement

We studied the atomic-level structure of a model Mg-MgH2 interface by means of the Car-Parrinello molecular dynamics method (CPMD). The interface was characterized in terms of total energy calculations, and an estimate of the work of adhesion was given, in good agreement with experimental results on similar systems. Furthermore, the interface was studied in a range of temperatures of interest for the desorption of hydrogen. We determined the diffusivity of atomic hydrogen as a function of the temperature, and give an estimate of the desorption temperature.

New module for channeling radiation simulation in Geant4

2021 ◽  
Vol 16 (12) ◽  
pp. P12042
Author(s):  
A.A. Savchenko ◽  
W. Wagner
Keyword(s):  
Experimental Data ◽  
Single Crystals ◽  
Dipole Approximation ◽  
Relativistic Electrons ◽  
Planar Channeling ◽  
Classical Approach ◽  
Electrons And Positrons ◽  
Simulation Results ◽  
Channeling Radiation ◽  
Good Agreement

Abstract We present a new C++ module for simulation of channeling radiation to be implemented in Geant4 as a discrete physical process. The module allows simulation of channeling radiation from relativistic electrons and positrons with energies above 100 MeV for various types of single crystals. In this paper, we simulate planar channeling radiation applying the classical approach in the dipole approximation as a first attempt not yet considering other contributory processes. Simulation results are proved to be in a rather good agreement with experimental data.

scholarly journals Molecular Dynamics Modellization and Simulation of Water Diffusion through Plant Cutin

1999 ◽  
Vol 54 (11) ◽  
pp. 896-902 ◽  
Author(s):  
Antonio Matas ◽  
Antonio Heredia
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Structural Information ◽  
Md Simulations ◽  
Water Molecules ◽  
Plant Cuticle ◽  
X Ray Diffraction ◽  
Cross Link ◽  
X Ray ◽  
Good Agreement

Abstract A theoretical molecular modelling study has been conducted for cutin, the biopolyester that forms the main structural component of the plant cuticle. Molecular dynamics (MD) simulations, extended over several ten picoseconds, suggests that cutin is a moderately flexible netting with motional constraints mainly located at the cross-link sites of functional ester groups. This study also gives structural information essentially in accordance with previously reported experimental data, obtained from X -ray diffraction and nuclear magnetic resonance experiments. MD calculations were also performed to simulate the diffusion of water mole­cules through the cutin biopolymer. The theoretical analysis gives evidence that water perme­ation proceedes by a “hopping mechanism”. Coefficients for the diffusion of the water molecules in cutin were obtained from their mean-square displacements yielding values in good agreement with experimental data.

scholarly journals Relationship between the Transport Coefficients of Polar Substances and Entropy

Entropy ◽  
2019 ◽  
Vol 22 (1) ◽  
pp. 13
Author(s):  
Ivan Anashkin ◽  
Sergey Dyakonov ◽  
German Dyakonov
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Diffusion Coefficient ◽  
High Pressures ◽  
Thermal Conductivity Coefficient ◽  
Good Description ◽  
Transport Coefficients ◽  
Viscosity Coefficient ◽  
Wide Region ◽  
Good Agreement

An expression is proposed that relates the transport properties of polar substances (diffusion coefficient, viscosity coefficient, and thermal conductivity coefficient) with entropy. To calculate the entropy, an equation of state with a good description of the properties in a wide region of the state is used. Comparison of calculations based on the proposed expressions with experimental data showed good agreement. A deviation exceeding 20% is observed only in the region near the critical point as well as at high pressures.

Simulation on Coal Devolatilization Combined a Multi-Step Kinetic Model with Chemkin Software

2012 ◽  
Vol 608-609 ◽  
pp. 1375-1382
Author(s):  
Rui Zhang ◽  
Qin Hui Wang ◽  
Zhong Yang Luo ◽  
Meng Xiang Fang
Keyword(s):  
Experimental Data ◽  
Kinetic Model ◽  
Intermediate Product ◽  
Coal Combustion ◽  
Model Complexity ◽  
Coal Pyrolysis ◽  
Simple Application ◽  
Calculation Results ◽  
Simulation Results ◽  
Good Agreement

As the first step in coal combustion and gasification, coal devolatilization has significant effect on reaction process. Previous coal devolatilization models have some disadvantages, such as poor flexibility, model complexity, and requirement of characterization parameters. Recently, Sommariva et al. have proposed a multi-step kinetic model of coal devolatilization. This model avoids the disadvantages mentioned above and can predict elemental composition of tar and char. In this paper, the mechanism of this model has been revised for simple application to Chemkin. Revision method is that some reactions are split into more reactions by using one pseudo-intermediate-product to replace several final products. Simulation results show that calculation results from revised mechanism compare quite well with that from original mechanism and have good agreement with experimental data. The revised mechanism is accurate and can be applied to Chemkin very easily, which gives it wide application to simulation of coal pyrolysis, gasification and combustion.

Characterization of effects of selected organic substances on decomposition of hydrogen peroxide during Fenton reaction

2004 ◽  
Vol 49 (4) ◽  
pp. 129-134 ◽  
Author(s):  
K.C. Namkung ◽  
A. Aris ◽  
P.N. Sharratt
Keyword(s):  
Experimental Data ◽  
Hydrogen Peroxide ◽  
Fenton Reaction ◽  
Reactive Black 5 ◽  
Organic Substances ◽  
Oxidation Model ◽  
Simulation Results ◽  
Good Agreement

This study aims to investigate the effects of selected organic substances on the degradation of hydrogen peroxide during the Fenton reaction. Since the presence of organic substances can strongly affect the mechanism of the Fenton reaction, the information on effects of organic substances on the reaction would be a vital guide to the success of its application to the destruction of organics in wastewater. Several organic compounds having different structures were selected as model pollutants: 4-chlorophenol, 1,4-dioxane, chloroform, a dye (reactive black-5), and EDTA. Oxidation of 4-chlorophenol and reactive black-5 resulted in enormously fast degradation of hydrogen peroxide, while others such as 1,4-dioxane and chloroform showed much slower degradation. These experimental data were compared to simulation results from a computational model based on a simple áOH-driven oxidation model. Modelling results for chloroform and 1,4-dioxane were in relatively good agreement with the experimental data, while those for 4-chlorophenol and reactive black-5 were very different from the experimental data. The results for EDTA showed a different trend to those for other compounds. From these results, classification of organic substances into several sub-groups was tried.

In-plane Thermal and Electronic Transport in Quantum Dot Superlattice

2001 ◽  
Vol 677 ◽  
Author(s):  
A. Khitun ◽  
J.L. Liu ◽  
K.L. Wang ◽  
G. Chen
Keyword(s):  
Experimental Data ◽  
Thermal Properties ◽  
Quantum Dot ◽  
Electronic Transport ◽  
Lattice Thermal Conductivity ◽  
Phonon Transport ◽  
Host Materials ◽  
Simulation Results ◽  
Germanium Quantum Dots ◽  
Good Agreement

ABSTRACTWe present a theoretical model in order to describe both thermal and electronic in-plane transports in quantum dot superlattice. The model takes into account the modifications of electron and phonon transport due to the space confinement caused by the mismatch in electronic and thermal properties between dot and host materials. The developed model provides the analysis of the in-plane superlattice electronic and thermal properties versus quantum dot size and their arrangement. Numerical calculations were carried out for a structure that consists of multiple layers of Si with regimented germanium quantum dots. The simulation results of the lattice thermal conductivity are in a good agreement with experimental data.

MELTING CURVE OF SEMICONDUCTORS WITH DEFECTS: PRESSURE DEPENDENCE

2012 ◽  
Vol 26 (07) ◽  
pp. 1250050 ◽  
Author(s):  
VU VAN HUNG ◽  
LE DAI THANH
Keyword(s):  
High Pressure ◽  
Moment Method ◽  
High Pressures ◽  
Melting Curve ◽  
Statistical Moment ◽  
Negative Slope ◽  
Pressure Melting ◽  
New Equation ◽  
Good Agreement ◽  
Statistical Moment Method

The high-pressure melting curve of semiconductors with defects has been studied using statistical moment method (SMM). In agreement with experiments and with DFT calculations we obtain a negative slope for the high-pressure melting curve. We have derived a new equation for the melting curve of the defect semiconductors. The melting was investigated at different high pressures, and the SMM calculated melting temperature of Si, AlP, AlAs and GaP crystals with defects being in good agreement with previous experiments.

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