 |
| Titel |
Effects of Hydrostatic Pressure on the Elastic Anisotropy of SnO2 Polymorphs: A First-principles Approach |
| VerfasserIn |
Pratik Kumar Das, Nibir Mandal, Ashok Arya |
| Konferenz |
EGU General Assembly 2016
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250121905
|
| Publikation (Nr.) |
 EGU/EGU2016-796.pdf |
|
|
|
|
|
| Zusammenfassung |
| Cassiterite (SnO2) is the most important ore mineral used for extraction of metal tin. Using
DFT calculations we investigate the pressure-dependent variations of elastic anisotropy in the
following SnO2 phases: rutile-type (tetragonal; P42/mnm), CaCl2-type (orthorhombic;
Pnnm)-, α-PbO2-type (orthorhombic; Pbcn)-, and fluorite-type (cubic; Fm-3m). We
estimate the shear anisotropy (A1 and A3) on {100} and {001} crystallographic
planes of the tetragonal phase, and (A1, A2 and A3) on {100}, {010} and {001}
crystallographic planes of the orthorhombic phases. The rutile-type phase shows strongest
shear anisotropy on the {001} planes (A2 > 4.8), and the degree of anisotropy
increases nonlinearly with pressure. Conversely, the anisotropy is almost absent
on the {100} planes (i.e. A1 ∼ 1) irrespective of the pressure. The CaCl2-type
phase exhibits similar shear anisotropy behavior preferentially on {001} (A3 >
5), while A1 and A2 remain close to 1. The α-PbO2-type phase shows strikingly
different elastic anisotropy characterized by a reversal in anisotropy (A3 > 1 to
< 1) with increasing pressure at a threshold value of 38 GPa. Furthermore, we
show that the electronic density of states and atomic configuration is crucial for
this pressure-dependent reversal in shear anisotropy. The DOS of α-PbO2-type
structure at 40 GPa exhibits multi-peaked structure of the valence band which is
indicative of underlying layered structure, which corresponds to the anisotropy
reversal. Our study also analyzes the directional Young’s moduli for the tetragonal and
orthorhombic phases as a function of pressure. The rutile-type SnO2 phase is the stiffest
material due to its high Young’s modulus, while fluorite-type SnO2has the lowest
stiffness. The directional Young’s moduli of both rutile -type and CaCl2 -type, is very
pressure sensitive along the diagonals in {001} plane. Furthermore, in the case of
α-PbO2, the Young’s modulus is pressure sensitive on {100} and {010}, rather than
{001}.
Bibliography
E. Deligoz, K. Colakoglu, Y.O. Cliftci, J. Phys. Chem. Solids 69 (2008) 859.
P. Ravindran, L. Fast, P.A. Korzhavyi, B. Johnnsson, J. Wills, O. Eriksson, J. Appl. Phys.
84 (1998) 4891.
R. A. Casali, J. Lasave, M. A. Caravaca, S. Koval, C. A. Ponce, R. L. Migoni, J. Phys.:
Condens. Matter. 25 (2013) 135404. |
|
|
|
|
|
|