tailieunhanh - Microstructural and Dynamical Heterogeneity Characteristics in Al2O3- 2SiO2 Liquid

In this paper the structural and dynamical characteristics in alumina- silicate Al2O3– 2SiO2 (AS2) liquid are investigated by molecular simulation method. Structural properties are clarified through the pair radial distribution function, distribution of TOn (T= Si, Al) coordination units and distribution of partial bond angle in TOn. Furthermore the change in diffusion mechanism between low and high pressure is revealed by transition of the structural units TOx → TOx±1. At the lowpressure, liquid AS2 exhibits the dynamics heterogeneity (DH). The origin of dynamic heterogeneity is identified and liquid AS2 consists of separate mobile and immobile regions. | VNU Journal of Science: Mathematics – Physics, Vol. 34, No. 1 (2018) 25-32 Microstructural and Dynamical Heterogeneity Characteristics in Al2O3- 2SiO2 Liquid Nguyen Thi Thanh Ha1,*, Kankham Keopanya2, Le Van Vinh1 1 Department of Computational Physics, Hanoi University of Science and Technology, Vietnam 2 Department of Physics, Thai Nguyen University of Education, Thai Nguyen, Vietnam Received 06 September 2017 Revised 23 October 2017; Accepted 31 October 2017 Abstract: In this paper the structural and dynamical characteristics in alumina- silicate Al2O3– 2SiO2 (AS2) liquid are investigated by molecular simulation method. Structural properties are clarified through the pair radial distribution function, distribution of TOn (T= Si, Al) coordination units and distribution of partial bond angle in TOn. Furthermore the change in diffusion mechanism between low and high pressure is revealed by transition of the structural units TOx → TOx±1. At the lowpressure, liquid AS2 exhibits the dynamics heterogeneity (DH). The origin of dynamic heterogeneity is identified and liquid AS2 consists of separate mobile and immobile regions. Keywords: Molecular dynamic, structure, dynamics heterogeneity, diffusion, network structure. 1. Introduction Silicate, glass-forming mixtures of SiO2 with an oxide such as Al2O3, Na2O, or K2O are an important class of materials used in many technological applications [1-4]. Therefore the microstructure and dynamical properties of liquid silicates have been studied by many experiments, theory and simulation. The results show that the structure of silicates consists of basic structural units TOx (x = 4,5,6) and the coordination units TO4 are dominant at ambient pressure. With increasing pressure, there is a gradual transformation from tetrahedral to octahedral network structure, bridging oxygen bonds are being broken [5-8]. The T–O–T bond angle reduces and the average coordination number of Al increases. At high pressure, the coordinated units .