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A molecular dynamics simulation requires the definition of a potential function, or a description of the terms by which the particles in the simulation will interact. In chemistry and biology this is usually referred to as a force field and in materials physics as an interatomic potential.
For a system of particles with masses , with coordinates = that constitute a time-dependent random variable, the resulting Langevin equation is [2] [3] ¨ = ˙ + (), where () is the particle interaction potential; is the gradient operator such that () is the force calculated from the particle interaction potentials; the dot is a time derivative ...
The various branches of the DEM family are the distinct element method proposed by Peter A. Cundall and Otto D. L. Strack in 1979, [5] the generalized discrete element method, [6] the discontinuous deformation analysis (DDA) and the finite-discrete element method concurrently developed by several groups (e.g., Munjiza and Owen).
In an ab initio MD simulation, the total energy of the system is calculated at each time step using density functional theory (DFT) or another method of quantum chemistry. The forces acting on each atom are then determined from the gradient of the energy with respect to the atomic coordinates, and the equations of motion are solved to predict ...
Brownian motion is the random motion of particles suspended in a medium (a liquid or a gas). [2] This motion pattern typically consists of random fluctuations in a particle's position inside a fluid sub-domain, followed by a relocation to another sub-domain. Each relocation is followed by more fluctuations within the new closed volume.
The methods listed here are among the most common and the most directly tied to materials science specifically, where atomistic and electronic structure calculations are also widely used in computational chemistry and computational biology and continuum level simulations are common in a wide array of computational science application domains.
Dissipative particle dynamics (DPD) is an off-lattice mesoscopic simulation technique [1] which involves a set of particles moving in continuous space and discrete time. Particles represent whole molecules or fluid regions, rather than single atoms, and atomistic details are not considered relevant to the processes addressed.
A computer simulation of high velocity air flow around the Space Shuttle during re-entry A simulation of the Hyper-X scramjet vehicle in operation at Mach-7. The fundamental basis of almost all CFD problems is the Navier–Stokes equations, which define many single-phase (gas or liquid, but not both) fluid flows.