Minimum energy configurations

Nature ◽  
1986 ◽  
Vol 319 (6053) ◽  
pp. 454-454 ◽  
Author(s):  
M.G. CALKIN ◽  
D. KIANG ◽  
D.A. TINDALL
1979 ◽  
Vol 57 (5) ◽  
pp. 538-551 ◽  
Author(s):  
Peeter Kruus ◽  
Barbara E. Poppe

A model of solutions of alkali halides in DMSO is developed. Each ion is described by a radius, a charge, a polarizability, and an exponential repulsion parameter. Each molecule is described by a polarizability, charges, 6-12 energy parameters, and 6-12 distance parameters centered on each of the 10 atoms in the molecule. The model is applied to calculate (i) the vaporization energy of solvent molecules, (ii) single ion solvation energies and configurations of the solvating molecules, and (iii) the energy as a function of reaction coordinate for the formation of an ion pair. The energies and configurations are obtained by allowing the systems to relax to minimum energy configurations by allowing motion of the molecules. The results of (i) give a vaporization energy 60% of the experimental. The results of (ii) give solvation energies in reasonable agreement with the experimental, and configurations which are reasonable from the point of view of mobilities of ions. The results of (iii) show the presence of a distinct solvent separated ion pair which actually has an energy lower than the contact ion pair. Advantages and problems involved in using this approach to model solutions are discussed.


Soft Matter ◽  
2008 ◽  
Vol 4 (7) ◽  
pp. 1396 ◽  
Author(s):  
Gernot J. Pauschenwein ◽  
Gerhard Kahl

1996 ◽  
Vol 64 (1) ◽  
pp. 157-174 ◽  
Author(s):  
Vittorio Murino ◽  
Carlo S. Regazzoni ◽  
Gian Luca Foresti

2004 ◽  
Vol 16 (23) ◽  
pp. 4165-4175 ◽  
Author(s):  
M F Vaz ◽  
S J Cox ◽  
M D Alonso

Author(s):  
B. D. Simmons ◽  
J. I. Hochstein ◽  
J. G. Marchetta ◽  
S. H. Collicott

Magnetic positive propellant positioning (MP3) of cryogenic propellants in spacecraft tanks may outperform existing technologies and, unlike some of the competing technologies, MP3 can be an adaptive management system that optimizes performance for the entire mission profile. Surface Evolver, (SE), a public domain program that seeks minimum energy configurations for modeled systems, provided a foundation on which to build a computational simulation to begin investigating the promise of MP3. Energies modeled include surface tension, potential energy due to background acceleration, and the change in potential energy due to the presence of a fluid in a magnetic field. A detailed development of these models is presented as well as specific expressions that other researchers can use with SE to study MP3. Verification and validation of the comprehensive model has been performed using several “known” solutions, three of which are reported herein: a constant gradient, a current carrying wire, and a dipole magnetic field. The computational tool is then used to study the ability of a magnet to retain a pool of LO2 about it when subjected to background acceleration. Results from this study, presented herein, indicate the promise of MP3 for adaptive cryogenic propellant management systems for future spacecraft and fuel depot applications.


Symmetry ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 158
Author(s):  
Pablo Negrón-Marrero ◽  
Melissa López-Serrano

In this paper, we consider the problem of characterizing the minimum energy configurations of a finite system of particles interacting between them due to attractive or repulsive forces given by a certain intermolecular potential. We limit ourselves to the cases of three particles arranged in a triangular array and that of four particles in a tetrahedral array. The minimization is constrained to a fixed area in the case of the triangular array, and to a fixed volume in the tetrahedral case. For a general class of intermolecular potentials we give conditions for the homogeneous configuration (either an equilateral triangle or a regular tetrahedron) of the array to be stable that is, a minimizer of the potential energy of the system. To determine whether or not there exist other stable states, the system of first-order necessary conditions for a minimum is treated as a bifurcation problem with the area or volume variable as the bifurcation parameter. Because of the symmetries present in our problem, we can apply the techniques of equivariant bifurcation theory to show that there exist branches of non-homogeneous solutions bifurcating from the trivial branch of homogeneous solutions at precisely the values of the parameter of area or volume for which the homogeneous configuration changes stability. For the triangular array, we construct numerically the bifurcation diagrams for both a Lennard–Jones and Buckingham potentials. The numerics show that there exist non-homogeneous stable states, multiple stable states for intervals of values of the area parameter, and secondary bifurcations as well.


Sign in / Sign up

Export Citation Format

Share Document