1,366 research outputs found
Double Exchange model for nanoscopic clusters
We solve the double exchange model on nanoscopic clusters exactly, and
specifically consider a six-site benzene-like nanocluster. This simple model is
an ideal testbed for studying magnetism in nanoclusters and for validating
approximations such as the dynamical mean field theory (DMFT). Non-local
correlations arise between neighboring localized spins due to the Hund's rule
coupling, favoring a short-range magnetic order of ferro- or antiferromagnetic
type. For a geometry with more neighboring sites or a sufficiently strong
hybridization between leads and the nanocluster, these non-local correlations
are less relevant, and DMFT can be applied reliably.Comment: 9 pages, 9 figures, 1 tabl
Transient model of hydrogen/oxygen reactor
Numerical analysis of effects of transient response in catalytic ignition system to promote hydrogen-oxygen combustio
A Formalization of Robustness for Deep Neural Networks
Deep neural networks have been shown to lack robustness to small input
perturbations. The process of generating the perturbations that expose the lack
of robustness of neural networks is known as adversarial input generation. This
process depends on the goals and capabilities of the adversary, In this paper,
we propose a unifying formalization of the adversarial input generation process
from a formal methods perspective. We provide a definition of robustness that
is general enough to capture different formulations. The expressiveness of our
formalization is shown by modeling and comparing a variety of adversarial
attack techniques
Efficient and accurate determination of lattice-vacancy diffusion coefficients via non equilibrium ab initio molecular dynamics
We revisit the color-diffusion algorithm [P. C. Aeberhard et al., Phys. Rev.
Lett. 108, 095901 (2012)] in nonequilibrium ab initio molecular dynamics
(NE-AIMD), and propose a simple efficient approach for the estimation of
monovacancy jump rates in crystalline solids at temperatures well below
melting. Color-diffusion applied to monovacancy migration entails that one
lattice atom (colored-atom) is accelerated toward the neighboring defect-site
by an external constant force F. Considering bcc molybdenum between 1000 and
2800 K as a model system, NE-AIMD results show that the colored-atom jump rate
k_{NE} increases exponentially with the force intensity F, up to F values far
beyond the linear-fitting regime employed previously. Using a simple model, we
derive an analytical expression which reproduces the observed k_{NE}(F)
dependence on F. Equilibrium rates extrapolated by NE-AIMD results are in
excellent agreement with those of unconstrained dynamics. The gain in
computational efficiency achieved with our approach increases rapidly with
decreasing temperatures, and reaches a factor of four orders of magnitude at
the lowest temperature considered in the present study
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