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Diffusion mechanism in liquid MgO under high pressure

In our study, we used molecular dynamics simulation (MD) to study diffusion mechanism in liquid MgO at a temperature of 3800K at a pressure ranging from 0 to 25 GPa. The calculated results and analysis of dynamical properties, spatially heterogeneous dynamics and diffusion mechanisms in MgO liquids will be reported in detail in this work. | JOURNAL OF SCIENCE OF HNUE Mathematical and Physical Sci. 2012 Vol. 57 No. 7 pp. 124-133 This paper is available online at http stdb.hnue.edu.vn DIFFUSION MECHANISM IN LIQUID MgO UNDER HIGH PRESSURE Mai Thi Lan Nguyen Van Hong and Pham Khac Hung Department of Computational Physics Institute of Engineering Physics Ha Noi University of Science amp Technology Abstract. The diffusion mechanism in liquid MgO under pressure up to 25 GPa at a temperature of 3800K have been studied using molecular dynamics simulation MD . The results show that each atom undergoes a series of stages while associated with the unchanged structural unit M gOx or OM gy . The diffusivity strongly depends on the rate of transition in M gOx M gOx 1 and OM gy OM gy 1 . Under low pressure diffusion proceeds due to the transition with x 3 4 5 and y 3 4 5 but mainly x 4 and y 4. Under high-pressure diffusion in the sample proceeds due to a transition with x 4 5 6 and y 4 5 6 but mainly x 5 and y 5. Investigating the movement of atoms in liquid MgO shows the spatially heterogeneous dynamics. The diffusion coefficient of Mg and O atoms is also examined through mean square displacement. Structural stability the life time of basic structural units is investigated in detail in this work. Keywords MD simulation transition diffusion mechanism heterogeneous dynamics. 1. Introduction In recent years some research on microstructure and diffusion mechanisms in disordered materials has shown that the spatially heterogeneous dynamics SHD i.e. the atom displacement and local structural relaxation are non-uniformly distributed through space. Numerous approaches have been employed to study the dynamics in liquid including the Mode Coupling theory 1 and the Adam-Gibbs theory 2 . However the atomic mechanism behind those phenomena has not been successfully identified in these studies. SHD and the relation between dynamics and diffusion mechanism in liquids and glassy polymers have been shown in 3-5 and it is also .