Parallel Object Oriented MD Simulation Program for Long Time Simulations of Metallic Glasses and Undercooled Liquids
Abstract
The MD simulation program TABB is motivated by the need of long time simulations for the investigation of slow processes near the glass transition of glass forming alloys. TABB is written in C++ with a high degree of flexibility: TABB allows the use of any short ranged pair potentials or EAM potentials, by generating and using a spline representation of all functions and their derivatives. TABB supports several numerical integration algorithms like the Runge-Kotta or the modified Gear-predictor-corrector algorithm of order five. The boundary conditions can be chosen to resemble the geometry of bulk materials or films. The simulation box length or the pressure can be fixed for each dimension separately. TABB may be used in isokinetic, isoenergeric or canonic (with random forces) mode. TABB contains a simple instruction interpreter to easily control the parameters and options during the simulation. The same source code can be compiled either for workstations or for parallel computers. The main optimization goal of TABB is to allow long time simulations of medium or small sized systems. To make this possible, much attention is spent on the optimized communication between the nodes. TABB uses a domain decomposition procedure. To use many nodes with a small system, the domain size has to be small compared to the range of particle interactions. In the limit of many nodes for only few atoms, the bottle neck of communication is the latency time. TABB minimizes the number of pairs of domains containing atoms that interact between these domains. This procedure minimizes the need of communication calls between pairs of nodes. TABB decides automatically, to how many, and to which directions the decomposition shall be applied. E.g., in the case of one dimensional domain decomposition, the simulation box is only split into "slabs" along a selected direction. The three dimensional domain decomposition is best with respect to the number of interacting domains only for simulations with medium range interactions on machines with many nodes (112 and more). TABB uses a modified cell algorithm to update a neighbor list for the force evaluation where the cells are small compared to the interaction range and contain the atoms in a continuous array. The updates of the neighbor list and of the domain decomposition are carried out synchronously with a flexible frequency. A small Ni0.5Zr0.5 system near the glass transition can be computed over 1 μs using 2.5 fs time steps within less than one week on a T3E-900 machine. Some examples of the computational results will be presented 1.
- Publication:
-
Molecular Dynamics on Parallel Computers. Edited by GRASSBERGER P ET AL. Published by World Scientific Publishing Co. Pte. Ltd
- Pub Date:
- 2000
- DOI:
- 10.1142/9789812793768_0013
- Bibcode:
- 2000mdpc.conf..199B