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Zijian Hong

Publications and source records attributed to Zijian Hong.

21 records · Page 2Linked to original sources

Phase-field simulations of lithium dendrite growth with open-source software

Dendrite growth is a long-standing challenge that has limited the applications of rechargeable lithium metal electrodes. Here, we developed a grand potential based nonlinear phase-field model to study the electrodeposition of lithium as relevant for a lithium metal anode, using open-source software package MOOSE. The dynamic morphological evolution under large/small overpotential is studied in 2-dimensions, revealing important dendrite growth/stable deposition patterns. The corresponding temporal-spatial distributions of ion concentration, overpotential and driving force are studied, which demonstrate an intimate, dynamic competition between ion transport and electrochemical reactions, resulting in vastly different growth patterns. Given the importance of morphological evolution for lithium metal electrodes, wide-spread applications of phase-field models have been limited in part due to in-house or proprietary software. In order to spur growth of this field, we utilize an open-source software package and make all files available to enable future studies to study the many unsolved aspects related to morphology evolution for lithium metal electrodes.

cond-mat.mtrl-sci↗

Switchable polar spirals in tricolor oxide superlattices

There are increasing evidences that ferroelectric states at the nanoscale can exhibit fascinating topological structures including polar vortices and skyrmions,akin to those observed in the ferromagnetic systems. Here we report the discovery of a new type of polar topological structure,ordered array of nanoscale spirals in the tricolor ferroelectric superlattice system via phase field simulations. This polar spiral structure is composed of fine ordered semivortex arrays with vortex cores forming a wavy distribution. It is demonstrated that this tricolor system has an ultrahigh Curie temperature of 1000 K and a temperature of 650 K for the phase transformation from spiral structure to inplane orthorhombic domain structure, showing a greatly enhanced thermal stability than the recently discovered polar vortex lattices in the superlattice system. Moreover, the spiral structure has a net inplane polarization that could be switched by an experimentally feasible irrotational inplane field. The switching process involves a metastable vortex state, and is fully reversible.

cond-mat.mes-hall↗

Blowing Polar Skyrmion Bubbles in Oxide Superlattices

Particle-like topological structures such as skyrmions and vortices have garnered ever-increasing interests due to the rich physical insights and potential broad applications. Here we discover the reversible switching between polar skyrmion bubbles and ordered vortex arrays in ferroelectric superlattices under an electric field, reminiscent of the Plateau-Raleigh instability in fluid mechanics. Electric field phase diagram is constructed, showing wide stability window for the observed polar skyrmions. This study is a demonstration for the computational design of ferroelectric topological structures and field-induced topological phase transitions.

cond-mat.mes-hall↗