Pressure dependent structural heterogeneity in calcium silicate glass

This work presents a molecular dynamics simulation (MDS) of CaSiO3 glass using Born–Mayer–Huggins potentials. The structural organization and structural phase transition under compression as well as network structure of CaSiO3 are clarified through analysis and visualization of molecular dynamics simulation data.
Nội dung trích xuất từ tài liệu:
Pressure dependent structural heterogeneity in calcium silicate glass JOURNAL OF SCIENCE OF HNUE DOI: 10.18173/2354-1059.2016-0046 Mathematical and Physical Sci., 2016, Vol. 61, No. 7, pp. 165-175 This paper is available online at http://stdb.hnue.edu.vn PRESSURE-DEPENDENT STRUCTURAL HETEROGENEITY IN CALCIUM SILICATE GLASS Mai Thi Lan1 , Nguyen Thi Thanh Ha1 , Tran Thuy Duong1 , Nguyen Thi Thao2 and Nguyen Van Hong1 1 School of Engineering Physics, Hanoi University of Science and Technology 2 Hanoi University of Education Abstract. This work presents a molecular dynamics simulation (MDS) of CaSiO3 glass using Born–Mayer–Huggins potentials. The structural organization and structural phase transition under compression as well as network structure of CaSiO3 are clarified through analysis and visualization of molecular dynamics simulation data. The short-range order structure, intermediate-range order structure are investigated in detail through analysis the pair of radial distribution function, the coordination number distribution in TOn polyedra and OTm linkages (n = 4 ÷ 11; m = 2 ÷ 5; T = Si, Ca). Topology structure of TOn and OTm is also clarified by investigating bond angle and bond length distribution in TOn polyhedra and OTm linkages. Keywords: Structure, phase transition, polymerization, molecular dynamics simulation, CaSiO3 .1. Introduction Calcium silicate (CaSiO3 ) is one of the members of Pyroxene, which is the main componentof Basalt. The CaSiO3 is one of main components of the Earth’s lower mantle. It is theimportant component in the glass and ceramic materials [1-4]. Knowledge of structure of CaSiO3system in both glass and liquid states under high pressure is necessary for understanding aboutvolcanic activity, the physicochemical and thermal change of the Earth, as well as controllingand completing the process of new material fabrication technology. CaSiO3 system has widelybeen studied for a long time by both theoretical and experimental methods [1, 5-9]. However,experiment is usually difficult to do at high temperature and pressure due to the high meltingtemperature of CaSiO3 [5]. Available experimental data are mainly measured at the ambientcondition [10-13]. The density functional theory-based molecular dynamics simulation of Silicateliquids [1] showed that the liquid CaSiO3 structure changes significantly under compression. Atambient pressure, the Ca-O coordination number is mainly 5, 6 and 7; Si-O coordination numberis 4. However, at high pressure (120 GPa) the Ca-O coordination number increases to 8, 9, 10; Si-Ocoordination number increases to 6. The Ab-initio molecular dynamics calculation for CaSiO3perovskite at high pressure and temperature [6] showed the existence of three stable structuralReceived October 2, 2016. Accepted October 28, 2016.Contact Mai Thi Lan, e-mail address: lan.maithi@hust.edu.vn 165 Mai Thi Lan, Nguyen Thi Thanh Ha, Tran Thuy Duong, Nguyen Thi Thao and Nguyen Van Hongphases: orthorhombic, tetragonal and cubic. The MDS results about local structure of CaSiO3in [5] are in agreement with experimental Raman spectra. The Si-O mean coordination numberis 4. It builds up the stable SiO4 tetrahedra in CaSiO3 . Although it has been studied extensivelyfor a long time but topology structure of Si-O network as well as the local environment of Ca2+ ,Si4+ , O2+ ions and their change under compression are still in debate and it need to be studiedmore. This is also the motivation of our study in this work.2. Content2.1. Calculation method The Born-Mayer-Huggins interatomic potential for CaSiO3 glass Table 1. The potential parameters for CaSiO3 glass MDS Aij (eV) Bij (A˚ −1 ) ˚ Cij (eVA) Si-Si 5006070.785 12.5 0.00 Si-O 7363.700 5.2632 0.00 O-O 1621.734 3.3333 30.22 Si-Ca 39991599.000 10.8696 0.00 Ca-O 29353.157 4.7619 0.00 Ca-Ca 200790000.000 9.6154 0.00 The atomic interaction potential is employed in MDS significantly affect to calculationresults. The pair interaction potential has still widely been used because of its simplicity as buildingatomic model. Up to now, there have some ev ...