scholarly journals Hugoniot States and Mie–Grüneisen Equation of State of Iron Estimated Using Molecular Dynamics

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 664
Author(s):  
Yuntian Wang ◽  
Xiangguo Zeng ◽  
Huayan Chen ◽  
Xin Yang ◽  
Fang Wang ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Equation Of State ◽  
High Pressures ◽  
Theoretical Models ◽  
Md Simulations ◽  
Hugoniot Relation ◽  
Micromechanical Approach ◽  
Cold Energy ◽  
Hugoniot Curves ◽  
Cold Pressure

The objective of this study was to develop a micromechanical approach for determining the Mie–Grüneisen EOS parameters of iron under the Hugoniot states. The multiscale shock technique (MSST) coupled with molecular dynamics (MD) simulations was employed to describe the shocked Hugoniot relation of single-crystal (SC) and nanocrystalline (NC) iron under high pressures. The Mie–Grüneisen equation of state (EOS) parameters, the cold pressure (Pc), the cold energy (Ec), the Grüneisen coefficient (γ), and the melting temperature (Tm) are discussed. The error between SC and NC iron results was found to be less than 1.5%. Interestingly, the differences in Hugoniot state (PH) and the internal energy between SC and NC iron were insignificant, which shows that the effect of grain size (GS) under high pressures was not significant. The Pc and Ec of SC and NC iron calculated based on the Morse potential were almost the same with those calculated based on the Born–Mayer potential; however, those calculated based on the Born–Mayer potential were a little larger at high pressures. In addition, several empirical and theoretical models were compared for the calculation of γ and Tm. The Mie–Grüneisen EOSs were shown on the 3D contour space; the pressure obtained with the Hugoniot curves as the reference was larger than that obtained with the cold curves as the reference.

scholarly journals Sorption, Structure and Dynamics of CO2 and Ethane in Silicalite at High Pressure: A Combined Monte Carlo and Molecular Dynamics Simulation Study

Molecules ◽  
2018 ◽  
Vol 24 (1) ◽  
pp. 99 ◽  
Author(s):  
Siddharth Gautam ◽  
Tingting Liu ◽  
David Cole
Keyword(s):  
Molecular Dynamics ◽  
Monte Carlo ◽  
Time Scales ◽  
Rotational Motion ◽  
High Pressures ◽  
Sorption Isotherms ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Structure And Dynamics ◽  
Low Pressures

Silicalite is an important nanoporous material that finds applications in several industries, including gas separation and catalysis. While the sorption, structure, and dynamics of several molecules confined in the pores of silicalite have been reported, most of these studies have been restricted to low pressures. Here we report a comparative study of sorption, structure, and dynamics of CO2 and ethane in silicalite at high pressures (up to 100 bar) using a combination of Monte Carlo (MC) and molecular dynamics (MD) simulations. The behavior of the two fluids is studied in terms of the simulated sorption isotherms, the positional and orientational distribution of sorbed molecules in silicalite, and their translational diffusion, vibrational spectra, and rotational motion. Both CO2 and ethane are found to exhibit orientational ordering in silicalite pores; however, at high pressures, while CO2 prefers to reside in the channel intersections, ethane molecules reside mostly in the sinusoidal channels. While CO2 exhibits a higher self-diffusion coefficient than ethane at low pressures, at high pressures, it becomes slower than ethane. Both CO2 and ethane exhibit rotational motion at two time scales. At both time scales, the rotational motion of ethane is faster. The differences observed here in the behavior of CO2 and ethane in silicalite pores can be seen as a consequence of an interplay of the kinetic diameter of the two molecules and the quadrupole moment of CO2.

Pressure dependence of the Grüneisen parameter and melting temperature of some metals

2021 ◽  
pp. 2150255
Author(s):  
K. Sunil ◽  
D. Ashwini ◽  
Vijay S. Sharma
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Equation Of State ◽  
Pressure Dependence ◽  
High Pressures ◽  
Grüneisen Parameter ◽  
Thermal Equation ◽  
Gruneisen Parameter ◽  
Melting Temperatures ◽  
Volume Dependence

We have used a method for determining volume dependence of the Grüneisen parameter in the Lindemann law to study the pressure dependence of melting temperatures in case of 10 metals viz. Cu, Mg, Pb, Al, In, Cd, Zn, Au, Ag and Mn. The reciprocal gamma relationship has been used to estimate the values of Grüneisen parameters at different volumes. The results for melting temperatures of metals at high pressures obtained in this study using the Lindemann law of melting are compared with the available experimental data and also with the values calculated from the instability model based on a thermal equation of state. The analytical model used in this study is much simpler than the accurate DFT calculations and molecular dynamics.

Theoretical studies of structural stability at high pressure

1995 ◽  
Vol 73 (5-6) ◽  
pp. 253-257 ◽  
Author(s):  
John S. Tse ◽  
Dennis D. Klug
Keyword(s):  
Molecular Dynamics ◽  
High Pressure ◽  
First Principles ◽  
High Pressures ◽  
Structural Phase ◽  
Md Simulations ◽  
Quantum Molecular Dynamics ◽  
First Principles Calculations ◽  
Quantum Mechanical Effects ◽  
Structural Memory

Theoretical methods are indispensible for the study of matter at high pressure. In the last decade the development of accurate intermolecular potentials and the methodologies in classical molecular dynamics (MD) simulations have greatly facililated the applications of these methods to the study of structural phase transformamtions of solids at high pressures. More recently, it has been possible to incorporate quantum mechanical effects into MD calculations. This method eliminates a great deal of empiricism. These first principles calculations have not only reproduced the experimental results for phase transformations but also provided detailed mechanisms and in some cases predicted new structures that may be found at high pressures. The success of MD calculations is illustrated through a review of our studies of pressure-induced amorphization and phase transitions in SiO2 and TiO2, and the structural memory effect in several materials. Current applications using quantum molecular dynamics on ice are discussed.

Elasticity, Thermal Properties, and Molecular Dynamics Using Non-Empirical Tight-Binding

1997 ◽  
Vol 491 ◽  
Author(s):  
Ronald E. Cohen ◽  
Lars Stixrude ◽  
Evgeny Wasserman
Keyword(s):  
Molecular Dynamics ◽  
Thermal Properties ◽  
Equation Of State ◽  
Total Energy ◽  
High Pressures ◽  
Tight Binding ◽  
Rare Gases ◽  
Thermal Equation ◽  
Wide Range ◽  
A Cell

ABSTRACTWe have further developed and applied a new non-empirical tight-binding total energy model to properties of Si, Xe, and Fe at high pressures. We have studied elasticity of various phases of each of these, demonstrating that the new model is applicable to a wide range of materials, including semiconductors, rare gases, and transition metals. We have used the particle-in-a-cell method to study the thermal equation of state of hep Fe and find excellent agreement with the shock equation of state. A molecular dynamics code has been developed based on this method, and we have studied the properties of Fe liquid at high pressures.

scholarly journals Modeling giant planets and brown dwarfs

2010 ◽  
Vol 6 (S276) ◽  
pp. 473-474
Author(s):  
Andreas Becker ◽  
Nadine Nettelmann ◽  
Ulrike Kramm ◽  
Winfried Lorenzen ◽  
Martin French ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Density Functional Theory ◽  
High Pressure ◽  
Equation Of State ◽  
Density Functional ◽  
Brown Dwarfs ◽  
Md Simulations ◽  
Giant Planets ◽  
Functional Theory ◽  
State Data

AbstractWe present new results in modeling the interiors of Giant Planets (GP) and Brown Dwarfs (BD). In general models of the interior rely on equation of state data for planetary materials which have considerable uncertainties in the high-pressure domain. Our calculations are based on ab initio equation of state (EOS) data for hydrogen, helium, hydrogen-helium mixtures and water as the representative of all heavier elements or ices using finite-temperature density functional theory molecular dynamics (FT-DFT-MD) simulations. We compare results for the BD Gliese 229B calculated with Saumon-Chabrier-Van Horn EOS (SCVH95) and our EOS data.

Efficient Treatment of Fixed and Induced Dipolar Interactions

2000 ◽  
Vol 653 ◽  
Author(s):  
Celeste Sagui ◽  
Thoma Darden
Keyword(s):  
Molecular Dynamics ◽  
Md Simulations ◽  
Lagrangian Formalism ◽  
Dipolar Interactions ◽  
Time Step ◽  
Efficient Treatment ◽  
Particle Mesh Ewald ◽  
Fixed Charges ◽  
Self Consistency ◽  
Induced Dipoles

AbstractFixed and induced point dipoles have been implemented in the Ewald and Particle-Mesh Ewald (PME) formalisms. During molecular dynamics (MD) the induced dipoles can be propagated along with the atomic positions either by interation to self-consistency at each time step, or by a Car-Parrinello (CP) technique using an extended Lagrangian formalism. The use of PME for electrostatics of fixed charges and induced dipoles together with a CP treatment of dipole propagation in MD simulations leads to a cost overhead of only 33% above that of MD simulations using standard PME with fixed charges, allowing the study of polarizability in largemacromolecular systems.

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