arXiv subjects

Shifang Xiao

Publications and source records attributed to Shifang Xiao.

3 recordsLinked to original sources

arXiv2021

Pattern formation during nonequilibrium crystallization by classical-density-functional-based approach

Solidification pattern during nonequilibrium crystallization is among the most important microstructures in the nature and technical realms. Phase field crystal (PFC) model could simulate the pattern formation during equilibrium crystallization at atom scale, but cannot grasp the nonequilibrium ones due to the absence of proper elastic-relaxation time scale. In this work, we propose a minimal classical-density-functional-theory-based model for crystal growth in supercooled liquid. Growth front nucleation (GFN) and various nonequilibrium patterns, including the faceting growth, spherulite, dendrite and the columnar-to-equiaxed transition (CET) among others, are grasped at atom scale. It is amazing that, except for undercooling and seed spacing, seed distribution is key factor that determines the CET. Overall, two-stage growth process, i.e., the diffusion-controlled growth and the GFN-dominated growth, are identified. But, compared with the second stage, the first stage becomes too short to be noticed under the high undercooling. The distinct feature for the second stage is the dramatic increments of dislocations, which explains the amorphous nucleation precursor in the supercooled liquid. Transition time between the two stages at different undercooling are investigated. Crystal growth of BCC structure further confirms our conclusions.

cond-mat.mtrl-sci↗

arXiv2016

A New Embedded-Atom Method Approach Based On the p-th Moment Approximation

Large scale atomistic simulations with suitable interatomic potentials are widely employed by scientists or engineers of different areas. Quick generation of high-quality interatomic potentials is of urgent need under present circumstances, which largely relies on the developments of potential construction methods and algorithms in this area. Quantities of interatomic potential models have been proposed and parameterized with various methods, such as analytic method, force-matching approach and multi-object optimization method, in order to make the potentials more transferable. Without apparently lowing precisions for describing the target system, potentials of fewer fitting parameters (FPs) are somewhat more physically reasonable. Thus, studying methods of reducing FP number is helpful to understand the underline physics of simulated systems and generalize the construction methods to other similar systems. However, few reported works concentrate on methods of reducing the number of FPs without affecting precisions. In this work, the methods of reducing the FP number while keeping the precisions are discussed from two aspects. Firstly, the physical ideas of constructions of the embedded-atom method (EAM) potential model are modified to make the potential more robust, flexible and scalable without introducing too many FPs.Secondly, the smaller reference data set (SRD), compared with the target reference database for describing the mechanical behaviors of aluminum, is employed in our construction procedures.

cond-mat.mtrl-sci↗

arXiv2016

Atomistic modeling of the anomalous helium behaviors in vanadium

Ab initio calculations have been performed to clarify the primary behaviors of He atoms in vanadium and to generate the database for the development of the interatomic potential for V-He system within the framework of the"s-band"model.The calculated formation energies of the tetrahedral,octahedral and substitutional He defects,as well as those for He2,He3 and He2V clusters are reasonable when compared with relevant experimental results and ab initio calculations under the same conditions.The applicability of the present V-He potential for atomistic simulations to investigate the moving,clustering,and trapping of interstitial He atoms in vanadium are demonstrated.Similar to the results in iron and tungsten,the interstitial He atoms can migrate quickly in vanadium. However,He atoms aggregate into clusters with low binding energies,and the trapping of He atoms depend much on the pre-existing traps in vanadium.

cond-mat.mtrl-sci↗