Molecular Dynamics Study of Structural Transitions and Melting in Two Dimensions

1995 ◽  
Vol 408 ◽  
Author(s):  
L. L. Boyer
Keyword(s):  
Molecular Dynamics ◽  
Low Temperatures ◽  
Structural Transition ◽  
Lattice Strain ◽  
Hexagonal Lattice ◽  
Two Dimensions ◽  
Square Lattice ◽  
Pair Potentials ◽  
Molecular Dynamics Calculations ◽  
Simple Pair

AbstractSimple pair potentials are constructed which give hexagonal- or squarelattice ground states in two dimensions, depending on the value of a single parameter controlling the width of the potential well. Molecular dynamics calculations for free clusters of a few hundred particles are used to examine a structural transition from the square lattice, at low temperatures, to the hexagonal lattice at high temperatures. Another structural transition (melting) is identified by the onset of diffusion. The melting temperature is found to be a minimum near the point where the barrier between the two structures, as a function of lattice strain, is also a minimum.

Molecular Dynamics Simulations of Shock-Defect Interactions in Two-Dimensional Nonreactive Crystals

1992 ◽  
Vol 296 ◽  
Author(s):  
Robert S. Sinkovits ◽  
Lee Phillips ◽  
Elaine S. Oran ◽  
Jay P. Boris
Keyword(s):  
Molecular Dynamics ◽  
Hexagonal Lattice ◽  
Square Lattice ◽  
Two Dimensional ◽  
Connection Machine ◽  
Defect Sites ◽  
Principal Axes ◽  
Shock Motion ◽  
Defect Interactions ◽  
Dynamics Simulations

AbstractThe interactions of shocks with defects in two-dimensional square and hexagonal lattices of particles interacting through Lennard-Jones potentials are studied using molecular dynamics. In perfect lattices at zero temperature, shocks directed along one of the principal axes propagate through the crystal causing no permanent disruption. Vacancies, interstitials, and to a lesser degree, massive defects are all effective at converting directed shock motion into thermalized two-dimensional motion. Measures of lattice disruption quantitatively describe the effects of the different defects. The square lattice is unstable at nonzero temperatures, as shown by its tendency upon impact to reorganize into the lower-energy hexagonal state. This transition also occurs in the disordered region associated with the shock-defect interaction. The hexagonal lattice can be made arbitrarily stable even for shock-vacancy interactions through appropriate choice of potential parameters. In reactive crystals, these defect sites may be responsible for the onset of detonation. All calculations are performed using a program optimized for the massively parallel Connection Machine.

WINDING ANGLE DISTRIBUTION OF LATTICE TRAILS IN TWO DIMENSIONS

2000 ◽  
Vol 11 (04) ◽  
pp. 731-738 ◽  
Author(s):  
IKSOO CHANG
Keyword(s):  
Exponential Function ◽  
Low Temperatures ◽  
Gaussian Function ◽  
Two Dimensions ◽  
Square Lattice ◽  
Angle Distribution ◽  
Stretched Exponential ◽  
Self Avoiding Walks ◽  
Winding Angle ◽  
Infinite Temperature

The winding angle problem of two-dimensional lattice trails on a square lattice is studied intensively by the scanning Monte Carlo simulation at infinite, tricritical, and low-temperatures. The winding angle distribution PN(θ) and the even moments of winding angle [Formula: see text] are calculated for the lengths of trails up to N = 300. At infinite temperature, trails share the same universal winding angle distribution with self-avoiding walks (SAWs), which is a stretched exponential function close to a Gaussian function exp [-θ2/ln N] and [Formula: see text]. However, trails at tricritical and low-temperatures do not share the same winding angle distribution with SAWs. For trails, PN(θ) is described well by a stretched exponential function exp [-|θ|α/ln N] and [Formula: see text] with α ~ 1.69 which is far from being a Gaussian and also different from those of SAWs at Θ and low-temperatures with α ~ 1.54. We provide a consistent numerical evidence that the winding angle distribution for trails at finite temperatures may not be a Gaussian function, but, a nontrivial distribution, possibly a stretched exponential function. Our result also demonstrates that the universality argument between trails and SAWs at infinite and tricritical temperatures indeed persists to the distribution function of winding angle and its associated scaling behavior.

scholarly journals Der Druck bei molekular-dynamischen Simulationen von Ionenflüssigkeiten/ The Pressure in Molecular Dynamics Simulations of Ionic Liquids

1976 ◽  
Vol 31 (9) ◽  
pp. 1068-1072 ◽  
Author(s):  
L. Schäfer ◽  
A. Klemm
Keyword(s):  
Molecular Dynamics ◽  
Ionic Liquids ◽  
Kinetic Energy ◽  
Potassium Chloride ◽  
Molecular Dynamics Simulations ◽  
Correlation Functions ◽  
Pair Potentials ◽  
Auto Correlation ◽  
Molecular Dynamics Calculations ◽  
Dynamics Simulations

Abstract Precise molecular dynamics calculations on molten potassium chloride have been performed using Born-Mayer-Huggins pair potentials and periodic boxes containing 216 ions. It is found that the function (2 Ek - ψ)/3V, Ek being the kinetic energy, the instantaneous virial and V the volume, respectively, which on averaging yields the pressure, fluctuates by ± 2000 bar due to the fluctuations of the exponential term ψex of ψ .To base the calculated pressure and velocity auto-correlation functions on good statistics, it seems necessary to reduce these fluctuations by increasing the periodic boxes.

Molecular dynamics study of the alloy (N2)67(Ar)29

1985 ◽  
Vol 63 (10) ◽  
pp. 1270-1273 ◽  
Author(s):  
Shuichi Nosé ◽  
Michael L. Klein
Keyword(s):  
Molecular Dynamics ◽  
Low Temperature ◽  
Angular Velocity ◽  
Power Spectrum ◽  
Structural Transition ◽  
Rotational Diffusion ◽  
Velocity Autocorrelation Function ◽  
Reorientational Motion ◽  
Velocity Autocorrelation ◽  
Molecular Dynamics Calculations

Molecular dynamics calculations are used to investigate the effect of isobaric cooling on the hexagonal alloy (N2)67(Ar)29. Particular attention is given to the behavior of the reorientational motion of the N2 molecules. No orientational or structural transition was found to accompany the cooling from 60 to 10 K at either P = 4 × 103 or P = 1 × 103 bar (1 bar = 100 kPa). However, the power spectrum of the angular-velocity autocorrelation function clearly reveals the freezing out of rotational diffusion at low temperature.

LATTICE RELAXATION AND THERMAL EXPANSION AT NOBLE-GAS SURFACES: A MOLECULAR DYNAMICS AND LEED STUDY FOR KR(111)

1991 ◽  
Vol 05 (28) ◽  
pp. 1873-1881 ◽  
Author(s):  
U. ROMAHN ◽  
H. GÖBEL ◽  
W. SCHOMMERS ◽  
P. VON BLANCKENHAGEN
Keyword(s):  
Molecular Dynamics ◽  
Thermal Expansion ◽  
Temperature Dependence ◽  
Low Temperatures ◽  
Noble Gas ◽  
Pair Potential ◽  
Lattice Relaxation ◽  
Lattice Contraction ◽  
Molecular Dynamics Calculations

Results on interlayer spacings and their temperature dependence at the Kr(111) surface obtained by molecular dynamics calculations using a realistic pair potential and by LEED experiments are reported. Both methods yield a lattice contraction at low temperatures and, furthermore, an enhanced thermal expansion at the surface.

MOLECULAR DYNAMICS CALCULATIONS OF NEAR-CRITICAL LIQUID OXYGEN DROPLET SURFACE TENSION

2005 ◽  
Vol 15 (4) ◽  
pp. 413-422 ◽  
Author(s):  
Michael M. Micci ◽  
S. J. Lee ◽  
B. Vieille ◽  
C. Chauveau ◽  
Iskendar Gokalp
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Droplet Surface ◽  
Liquid Oxygen ◽  
Molecular Dynamics Calculations

Dynamics and kinetics of the Si(1D) + H2/D2 reactions on a new global ab initio potential energy surface

2021 ◽  
Vol 23 (10) ◽  
pp. 6141-6153
Author(s):  
Jianwei Cao ◽  
Yanan Wu ◽  
Haitao Ma ◽  
Zhitao Shen ◽  
Wensheng Bian
Keyword(s):  
Molecular Dynamics ◽  
Potential Energy ◽  
Potential Energy Surface ◽  
Ab Initio ◽  
Quantum Dynamics ◽  
Energy Surface ◽  
Molecular Dynamics Calculations ◽  
Ring Polymer ◽  
Ring Polymer Molecular Dynamics ◽  
Kinetics Of

Quantum dynamics and ring polymer molecular dynamics calculations reveal interesting dynamical and kinetic behaviors of an endothermic complex-forming reaction.

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