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Manuscript Title: Molecular dynamics program of order N for simulation of condensed matter systems II. MDSPNL: pyramid with neighbour list, short-range interactions.
Authors: Z.A. Rycerz
Program title: MDSPNL
Catalogue identifier: ABZC_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 61(1990)361
Programming language: Fortran.
Computer: CYBER 962-11.
Operating system: NOS/VE 1.5.1.
Word size: 64
Peripherals: disc.
Keywords: Molecular dynamics, Condensed matter Simulation, Solid state physics, Other.
Classification: 7.7.

Nature of problem:
Study of the thermodynamic, structural and dynamic properties of liquids or solids.

Solution method:
A system of N mutually interacting particles is simulated. The classical equations of motion are solved at successive time steps, at each of which the force acting upon each particle, due to its interaction with the other particles contained in the sphere of cut-off radius Rc, is calulated. Periodic Boundary Conditions (PBC) are applied to the system in order to make it pseudo-infinite. When the system reaches thermal equilibrium thermodynamic measurements are made by averaging over time. The basic quantities which are (or, optionally, can be) calculated directly in the program are: average temperature, potential energy, kinetic energy, total energy, virial internal pressure, radial distribution function, mean square displacement, diffusion coefficient and 4th moment of dynamic structure factor. Data such as coordinates, velocities and forces at successive time steps are saved for further analysis.

Restrictions:
In the present program the simulation is restricted to monoatomic systems in which the particles interact by simple, central short-range forces. Because the cpu time depends linearly on the number of particles, there are no special restrictions on the size of the simulated system. Depending on available computer memory and computer speed, N may change from about 10**2 to 10**5 (or more) particles.

Running time:
The over-all program speed (or cpu time) depends mainly on the size of the system (N), the value of Rc and the value of NTUPDA parameter which specifies how often the nearest neighbour list is updated; for example for Rc chosen as above (=CUBL(N=64)/2), the MDSPNL program attains on the Cyber 962 the speed of 5200 and 5500 p/s for NTUPDA = 10 and 20, respectively, which is approximately ten times more than the speed of the Link Cell (LC) method. Therefore, the cpu time for runs of 1000 time steps with N = 1000 and 21952 are roughly equal to 3 min and 70 min, respectively.