56 research outputs found
Non-monotonic behavior of the Binder Parameter in the discrete spin systems
We study a non-monotonic behavior of the Binder parameter, which appears in
the discrete spin systems. Using the Fortuin-Kasteleyn graph representation, we
find that the improved estimator of the Binder parameter consists of two terms
with values only in high- and low-temperature regions. The non-monotonic
behavior is found to originate from the low-temperature term. With the
appropriately defined order parameter, we can reduce the influence of the
low-temperature term, and as a result, the non-monotonic behavior can also be
reduced. We propose new definitions of the order parameter, which reduces or
eliminates the non-monotonic behavior of the Binder parameter in a system for
which the improved estimator of the Binder parameter is unknown.Comment: 23 pages, 12 figures, added new result
Configuration sampling in multi-component multi-sublattice systems enabled by ab Initio Configuration Sampling Toolkit (abICS)
Simulation of the intermediate levels of disorder found in multi-component
multi-sublattice systems in various functional materials is a challenging
issue, even for state-of-the-art methodologies based on first-principles
calculation. Here, we introduce our open-source package ab Initio Configuration
Sampling Toolkit (abICS), which combines high-throughput first-principles
calculations, machine learning, and parallel extended ensemble sampling in an
active learning setting to enable such simulations. The theoretical background
is reviewed in some detail followed by brief notes on usage of the software. In
addition, our recent applications of abICS to multi-component ionic systems and
their interfaces for energy applications are reviewed as demonstration of the
power of this approach.Comment: 25 pages, 6 figure
Data-analysis software framework 2DMAT and its application to experimental measurements for two-dimensional material structures
An open-source data-analysis framework 2DMAT has been developed for
experimental measurements of two-dimensional material structures. 2DMAT| offers
five analysis methods: (i) Nelder-Mead optimization, (ii) grid search, (iii)
Bayesian optimization, (iv) replica exchange Monte Carlo method, and (v)
population-annealing Monte Carlo method. Methods (ii) through (v) are
implemented by parallel computation, which is efficient not only for personal
computers but also for supercomputers. The current version of 2DMAT is
applicable to total-reflection high-energy positron diffraction (TRHEPD),
surface X-ray diffraction (SXRD), and low-energy electron diffraction (LEED)
experiments by installing corresponding forward problem solvers that generate
diffraction intensity data from a given dataset of the atomic positions. The
analysis methods are general and can be applied also to other experiments and
phenomena.Comment: 11 pages, 8 figure
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