136 research outputs found
A tool for parameter-space explorations
A software for managing simulation jobs and results, named "OACIS", is
presented. It controls a large number of simulation jobs executed in various
remote servers, keeps these results in an organized way, and manages the
analyses on these results. The software has a web browser front end, and users
can submit various jobs to appropriate remote hosts from a web browser easily.
After these jobs are finished, all the result files are automatically
downloaded from the computational hosts and stored in a traceable way together
with the logs of the date, host, and elapsed time of the jobs. Some
visualization functions are also provided so that users can easily grasp the
overview of the results distributed in a high-dimensional parameter space.
Thus, OACIS is especially beneficial for the complex simulation models having
many parameters for which a lot of parameter searches are required. By using
API of OACIS, it is easy to write a code that automates parameter selection
depending on the previous simulation results. A few examples of the automated
parameter selection are also demonstrated.Comment: 4 pages, 5 figures, CSP 2014 conferenc
Dynamical Study of Polydisperse Hard-Sphere System
We study the interplay between the fluid-crystal transition and the glass
transition of elastic sphere system with polydispersity using nonequilibrium
molecular dynamics simulations. It is found that the end point of the
crystal-fluid transition line, which corresponds to the critical polydispersity
above which the crystal state is unstable, is on the glass transition line.
This means that crystal and fluid states at the melting point becomes less
distinguishable as polydispersity increases and finally they become identical
state, i.e., marginal glass state, at critical polydispersity.Comment: 5 pages, 5 figure
Positional Order and Diffusion Processes in Particle Systems
Nonequilibrium behaviors of positional order are discussed based on diffusion
processes in particle systems. With the cumulant expansion method up to the
second order, we obtain a relation between the positional order parameter
and the mean square displacement to be with a reciprocal vector and the dimension of the system .
On the basis of the relation, the behavior of positional order is predicted to
be when the system involves normal diffusion
with a diffusion constant . We also find that a diffusion process with
swapping positions of particles contributes to higher orders of the cumulants.
The swapping diffusion allows particle to diffuse without destroying the
positional order while the normal diffusion destroys it.Comment: 4 pages, 4 figures. Submitted to Phys. Rev.
Static and dynamical aspects of the metastable states of first order transition systems
We numerically study the metastable states of the 2d Potts model. Both of
equilibrium and relaxation properties are investigated focusing on the finite
size effect. The former is investigated by finding the free energy extremal
point by the Wang-Landau sampling and the latter is done by observing the
Metropolis dynamics after sudden heating. It is explicitly shown that with
increasing system size the equilibrium spinodal temperature approaches the
bistable temperature in a power-law and the size-dependence of the nucleation
dynamics agrees with it. In addition, we perform finite size scaling of the
free energy landscape at the bistable point.Comment: 8 pages, 6 figures, submitted to Physics Procedia as a proceedings of
the 24th Annual CSP Workshop at the University of Georgi
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