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The diffusion coefficient is found to be a product of the rate of LDF and mean square displacement of Fe particles per LDF. The diffusion is realized by two types of activated LDFs. First type is accompanied by frequent back-and-forth movements of Fe particles. The second type causes the random movement of Fe particles. | JOURNAL OF SCIENCE OF HNUE Mathematical and Physical Sci. 2014 Vol. 59 No. 7 pp. 112-118 This paper is available online at http stdb.hnue.edu.vn LOCAL DENSITY FLUCTUATIONS IN SIMULATED LIQUID IRON Nguyen Thi Thao1 Pham Khac Hung2 and Le Van Vinh2 1 Faculty of Physics Hanoi National University of Education 2 Faculty of Computational Physics Hanoi University of Science amp Technology Abstract. We present a result of a molecular dynamics MD simulation of liquid iron. A series of MD models containing 104 particles under periodic boundary conditions at temperatures from 290 to 2300 K have been constructed. We focus on local density fluctuations LDFs which enable the diffusion of iron particles. We found that LDFs operate as a diffusion vehicle for Fe particles. The diffusion coefficient is found to be a product of the rate of LDF and mean square displacement of Fe particles per LDF. The diffusion is realized by two types of activated LDFs. First type is accompanied by frequent back-and-forth movements of Fe particles. The second type causes the random movement of Fe particles. Keywords Density fluctuations simulated liquid iron particles. 1. Introduction It is commonly accepted that density fluctuation enables the collective movement of particles in the liquid. The local density around the ith particle can be quantified as nOi ρi 1.1 VO 3 where VO 4πRO 3 nOi is the number of particles in a coordination sphere of the ith particle RO is the radius of the coordination sphere. If the number nOi changes then the local density around the ith particle varies. This means that the change of nOi at some moments represents the local density fluctuation LDF . The schematic illustration of LDF for selected particle is presented in Figure 1. It can be seen that LDFs happen four times for a selected particle. Therefore in the present study we investigate LDFs happening in Fe MD models. The structure of obtained liquids and amorphous solids has been also analyzed through the pair .
