PROGRAM SUMMARY
Title of program:
Fracture
Catalogue identifier:
ADKS
Ref. in CPC:
124(2000)60
Distribution format: tar gzip file
Operating system: UNIX
High speed store required:
2MK words
Number of lines in distributed program, including test data, etc:
2821
Programming language used: C
Computer: DEC ALPHA 300
Nature of physical problem:
In a typical research activity involving simulations of complex physical
systems, one is often faced with a 'research loop', which may be loosely
described as follows: definition of input data; running of a
simulation, outputting data to a storage disk; post-processing of the
accumulated data for extracting relevant information with the eventual
aid of graphics and numerical packages; definition of new input
parameters and, closing the loop, starting a new simulation run.
Advances in computer hardware, mainly faster processors, and the
increased availability of software development tools, with plenty of
graphics resources, have been markedly increasing the feasibility of
alternative solutions for improving the above scheme.
Method of solution
Interactive simulations offer an attractive option for the study of
systems in which a great deal of feedback, in the sense described above,
is required. They are also ideal for teaching purposes. The present
program gives an illustration of an interactive simulation environment.
The dynamical behaviour of a two-dimensional Lennard-Jones 'solid' under
stress, with either a grain boundary or an initial crack, is simulated
through a molecular dynamics algorithm.
Restrictions on the complexity of the problem
The interactiveness concept strongly relies on the display of an
animated graphical representation of the system. The quality of the
animation depends on the rate with which frames are displayed on the
graphical display window. This rate, in its turn, depends on the
iteration time of the simulation algorithm. Hence, the size of the
systems which may be investigated, while maintaining an acceptable
animation quality, depends on the machine processor. Systems with up to
50,000 atoms give fair animations for the target machine given above.
Subjecting the system to strain rates sufficiently high for inducing
atomic displacements of the order of the mean inter-atomic distance in
one integration step will cause the program to collapse. Studies at
such high rates will require modifications of the MD algorithm. The
implementation of an adaptative integration method will, most possibly,
be enough for most applications.
Typical running time
The typical running time is machine and system size dependent.
Unusual features of the program
Although the program has been originally designed for illustrative
purposes, its final version incorporates features which, we believe,
render it in a good standard for research work in two-dimensional
models, provided a better treatment is given to thermal effects. In
particular, it has been endowed with a control which allows the user to
generate an instantaneous 'snapshot' of the graphics screen. The image
is stored in a bitmap file (X11 standard), created under the same
directory in which the program is running.
The graphical part relies on the MOTIF library.