J. I. Beltrán | Searcharxiv

arXiv2016

Landau modeling of dynamical nucleation of martensite at grain boundaries under local stress

The dynamical nucleation of martensite in polycrystals is simulated by means of Lagrange-Rayleigh dynamics with Landau energetics, which is capable of obtaining the local stress as a result of the interplay of the potential of transformation and external loadings. By monitoring the patio-temporal distribution of the strain in response to the local stress, we demonstrate that the postcursors, high angle grain boundaries and triple junctions act as favorable heterogeneous nucleation sites corresponding to different loading and cooling conditions, and predict the phase diagram of the nucleation mode of martensite.

cond-mat.mtrl-sci↗

arXiv2015

Tight-binding approach to penta-graphene

We introduce an effective tight-binding model to discuss penta-graphene and present an analytical solution. This model only involves the $π$-orbitals of the sp$^2$-hybridized carbon atoms and reproduces the two highest valence bands. By introducing energy-dependent hopping elements, originating from the elimination of the sp$^3$-hybridized carbon atoms, also the two lowest conduction bands can be well approximated - but only after the inclusion of a Hubbard onsite interaction as well as of assisted hopping terms. The eigenfunctions can be approximated analytically for the effective model without energy-dependent hopping elements and the optical absorption is discussed. We find large isotropic absorption of up to 24\% for transitions at the $Γ$-point, but the general absorption will show a strongly anisotropic behaviour depending on the linear polarization of the incident light.

cond-mat.mes-hall↗