Phase stability and pressure-induced structural transitions at zero temperature in ZnSiO3
and Zn2SiO4

doi:10.1088/0953-8984/21/48/485801

Phase stability and pressure-induced structural transitions at zero temperature in ZnSiO₃ and Zn₂SiO₄

S Zh Karazhanov et al 2009 J. Phys.: Condens. Matter 21 485801 (9pp) doi: 10.1088/0953-8984/21/48/485801

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S Zh Karazhanov^1,2,3,5, P Ravindran¹, P Vajeeston¹, A G Ulyashin^2,6, H Fjellvåg¹ and B G Svensson⁴
¹ Centre for Material Science and Nanotechnology, Department of Chemistry, University of Oslo, PO Box 1033 Blindern, N-0315 Oslo, Norway
² Institute for Energy Technology, PO Box 40, N-2027 Kjeller, Norway
³ Physical-Technical Institute, 2B Mavlyanov Street, Tashkent 700084, Uzbekistan
⁴ Department of Physics, University of Oslo, PO Box 1048 Blindern, N-0316 Oslo, Norway
⁵ Author to whom any correspondence should be addressed
⁶ Present address: SINTEF, Materials and Chemistry, PO Box 124 Blindern, N-0314 Oslo, Norway
E-mail: smagul.karazhanov@ife.no

Abstract. Using density functional total energy calculations the structural phase stability and pressure-induced structural transition in different polymorphs of ZnSiO₃ and Zn₂SiO₄ have been studied. Among the considered monoclinic phase with space groups (P 2₁/c) and (C 2/c), rhombohedral $(R\bar {3})$ and orthorhombic (Pbca) modifications the monoclinic phase (P 2₁/c) of ZnSiO₃ is found to be the most stable one. At high pressure monoclinic ZnSiO₃ (C 2/c) can co-exist with orthorhombic (Pbca) modification. Differences in equilibrium volume and total energy of these two polymorphs are very small, which indicates that it is relatively easier to transform between these two phases by temperature, pressure or chemical composition. It can also explain the experimentally established result of metastability of the orthorhombic phase under all conditions. The following sequence of pressure-induced structural phase transitions is found for ZnSiO₃ polymorphs: monoclinic $(P2_{1}/c) \to$ monoclinic $(C2/c) \to$ rhombohedral $(R\bar {3})$ . Among the rhombohedral ( $R\bar {3}$ ), tetragonal $(I\bar {4} 2d)$ , orthorhombic (Pbca), orthorhombic (Imma), cubic $(Fd\bar {3} m)$ and orthorhombic (Pbnm) modifications of Zn₂SiO₄, the rhombohedral phase is found to be the ground state. For this chemical composition of zinc silicate the following sequence of structural phase transitions is found: rhombohedral $(R\bar {3}) \to$ tetragonal $(I\bar {4} 2d) \to$ orthorhombic $(Pbca) \to$ orthorhombic (Imma) $\to$ cubic $(Fd\bar {3} m) \to$ orthorhombic (Pbnm). Based on the analogy of crystal structures of magnesium and zinc silicates and using the lattice and positional parameters of Mg₂SiO₄ as input, structural properties of spinel Zn₂SiO₄ have also been studied.