scholarly journals Crystal and electronic structure engineering of tin monoxide by external pressure

2021 ◽  
Author(s):  
Kun Li ◽  
Junjie Wang ◽  
Vladislav A. Blatov ◽  
Yutong Gong ◽  
Naoto Umezawa ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Band Gap ◽  
High Pressures ◽  
Low Pressure ◽  
Widespread Application ◽  
Space Group ◽  
Tin Monoxide ◽  
High Possibility ◽  
Pressure Phase

AbstractAlthough tin monoxide (SnO) is an interesting compound due to its p-type conductivity, a widespread application of SnO has been limited by its narrow band gap of 0.7 eV. In this work, we theoretically investigate the structural and electronic properties of several SnO phases under high pressures through employing van der Waals (vdW) functionals. Our calculations reveal that a metastable SnO (β-SnO), which possesses space group P21/c and a wide band gap of 1.9 eV, is more stable than α-SnO at pressures higher than 80 GPa. Moreover, a stable (space group P2/c) and a metastable (space group Pnma) phases of SnO appear at pressures higher than 120 GPa. Energy and topological analyses show that P2/c-SnO has a high possibility to directly transform to β-SnO at around 120 GPa. Our work also reveals that β-SnO is a necessary intermediate state between high-pressure phase Pnma-SnO and low-pressure phase α-SnO for the phase transition path Pnma-SnO →β-SnO → α-SnO. Two phase transition analyses indicate that there is a high possibility to synthesize β-SnO under high-pressure conditions and have it remain stable under normal pressure. Finally, our study reveals that the conductive property of β-SnO can be engineered in a low-pressure range (0–9 GPa) through a semiconductor-to-metal transition, while maintaining transparency in the visible light range.

scholarly journals Crystal and Electronic Structure Engineering of Tin Monoxide by External Pressure

2020 ◽  
Author(s):  
Kun Li ◽  
Junjie Wang ◽  
Vladislav A. Blatov ◽  
Yutong Gong ◽  
Naoto Umezawa ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Band Gap ◽  
Low Pressure ◽  
External Pressure ◽  
Widespread Application ◽  
Space Group ◽  
Tin Monoxide ◽  
High Possibility ◽  
Pressure Phase

Abstract Although tin monoxide (SnO) is an interesting compound due to its p-type conductivity, a widespread application of SnO has been limited by its narrow band gap of 0.7 eV. In this work, we theoretically investigate the structural and electronic properties of several SnO phases under high pressure through employing van der Waals (vdW) functionals. Our calculations reveal that a metastable SnO (A-SnO), which possesses space group P21/c and a wide band gap of 1.9 eV, is more stable than l-SnO at pressures higher than 80 GPa. Moreover, a stable (space group P2/c) and a metastable (space group Pnma) phases of SnO appear at pressures higher than 120 GPa. Energy and topological analyses show that P2/c-SnO has a high possibility to directly transform to t-SnO at around 120 GPa. Our work also reveals that h-SnO is a necessary intermediate state between high-pressure phase Pnma-SnO and low-pressure phase o-SnO for the phase transition path Pnma-SnO ®u-SnO ® g-SnO. Two phase transition analyses indicate that there is a high possibility to synthesize h-SnO under high-pressure conditions and have it remain stable under normal pressure. Finally, our study reveals that the conductive property of -SnO can be engineered in a low-pressure range (0-9 GPa) through a semiconductor-to-metal transition, while maintaining transparency in the visible light range.

LEAD-CHALCOGENIDES UNDER PRESSURE: AB-INITIO STUDY

2013 ◽  
Vol 22 ◽  
pp. 612-618 ◽  
Author(s):  
DINESH C. GUPTA ◽  
IDRIS HAMID
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Ab Initio ◽  
Band Gap ◽  
Rock Salt ◽  
High Pressures ◽  
Ambient Pressure ◽  
High Pressure Phase ◽  
Lead Chalcogenides ◽  
Pressure Phase

ab-initio calculations using fully relativistic pseudo-potential have been performed to investigate the high pressure phase transition, elastic and electronic properties of lead-chalcogenides including the less known lead polonium. The calculated ground state parameters, for the rock-salt structure show good agreement with the experimental data. The enthalpy calculations show that these materials undergo a first-order phase transition from rock-salt to CsCl structure at 19.4, 15.5, 11.5 and 7.3 GPa for PbS, PbSe, PbTe and PbPo, respectively. Present calculations successfully predicted the location of the band gap at L-point of Brillouin zone as well as the value of the band gap in every case at ambient pressure. It is observed that unlike other lead-chalcogenides, PbPo is semi-metal at ambient pressure. The pressure variation of the energy gap indicates that these materials metalized under high pressures. For this purpose, the electronic structure of these materials has also been computed in parent as well as in high pressure phase.

X-ray diffraction investigations of CaF2 at high pressure

1992 ◽  
Vol 25 (5) ◽  
pp. 578-581 ◽  
Author(s):  
L. Gerward ◽  
J. S. Olsen ◽  
S. Steenstrup ◽  
M. Malinowski ◽  
S. Åsbrink ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Synchrotron Radiation ◽  
High Pressures ◽  
Low Pressure ◽  
Single Crystal Sample ◽  
X Ray Diffraction ◽  
Crystal Sample ◽  
X Ray ◽  
Pressure Phase

Synchrotron-radiation X-ray diffraction studies of CaF2 at high pressures have been performed on a powder sample up to 45 GPa and on a single-crystal sample up to 9.4 GPa. The bulk modulus of the low-pressure phase was determined to be B 0 = 87 (5) GPa. A phase transition was observed at about 9.5 GPa. The transition is accompanied by a volume contraction of 11%. The high-pressure phase is orthorhombic PbCl2 type (space group Pbnm). The sample only partially reverts to the low-pressure phase upon release of pressure.

OPTICAL PROPERTIES OF ANATASE TiO2 UNDER THE HIGH PRESSURE

2001 ◽  
Vol 15 (28n30) ◽  
pp. 3952-3955 ◽  
Author(s):  
TAKAO SEKIYA ◽  
SHINSUKE OHTA ◽  
SUSUMU KURITA
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Optical Properties ◽  
Lower Energy ◽  
Luminescence Band ◽  
High Pressures ◽  
Anatase Tio2 ◽  
Broad Luminescence Band ◽  
Pressure Phase ◽  
Energy Side

Optical absorption, luminescence and Raman spectra were measured for anatase TiO 2 under high pressures. The pressure dependence of Raman frequencies is determined. The absorption edge of anatase shifts to higher energy side with increasing pressure and the edge jumps abruptly to lower energy side on the phase transition. A broad luminescence band of anatase shifts also to higher energy side with increasing pressure. These experimental results reveal that the pressure-induced phase transition from anatase to high-pressure phase arises in the range of 4.0-4.6 GPa.

First-principles studies of phase transition and structural stability of SrC2 under pressure

2014 ◽  
Vol 28 (24) ◽  
pp. 1450190 ◽  
Author(s):  
Yi-Lin Lu ◽  
Hui Zhao
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
First Principles ◽  
Phonon Dispersion ◽  
Covalent Bond ◽  
Text Structure ◽  
High Pressure Phase ◽  
Space Group ◽  
Type Space ◽  
Pressure Phase

Pressure-induced phase transitions in SrC 2 are investigated using the first-principles plane wave pseudopotential method within the generalized gradient approximation. The phase transition from monoclinic phase ( CaC 2-II-type, space group C2/c) to trigonal ( CaC 2-VII-type, space group [Formula: see text]) structure is predicted to occur at 10.4 GPa. The high-pressure phase is thermodynamic, mechanically and dynamically stable, as verified by the calculations of its formation energy, elastic stiffness constants and phonon dispersion. Further the electronic analysis predicates this high-pressure phase to be an insulator. When increasing pressure, the ionic bond between C and Sr is strengthened, as well is the covalent bond between C and C , however, the increase of the ionic interaction between Sr and C preponderates over that of the covalent bond interaction, so the gap is narrowed.

Discovery of γ-B28, a Novel Boron Allotrope with Partially Ionic Bonding

2011 ◽  
Vol 1307 ◽  
Author(s):  
Artem R. Oganov
Keyword(s):  
Phase Transition ◽  
Phase Diagram ◽  
High Pressure ◽  
Charge Transfer ◽  
High Pressures ◽  
Phonon Dispersion ◽  
Qualitative Difference ◽  
Light Element ◽  
Phonon Dispersion Curves ◽  
Pressure Phase

ABSTRACTγ-B28 is a recently discovered high-pressure phase of boron, with the structure consisting f icosahedral B12 clusters and B2 pairs in a NaCl-type arrangement: (B2)δ+(B12)δ-, and displaying a significant charge transfer δ~0.48. Boron is the only light element, for which the phase diagram has become clear only a few years ago, with the discovery of γ-B28, and this phase diagram is discussed here among other recent findings. γ-B28 was first experimentally obtained as a pure boron allotrope in early 2004 by J.H. Chen and V.L. Solozhenko (although a similar diffraction pattern was published in a 1965 by R.H. Wentorf, in a paper that until recently was believed to be wrong) and its unique structure was discovered by A.R. Oganov in 2006 with the use of the ab initio evolutionary algorithm USPEX (Oganov & Glass, 2006) and later confirmed by other studies. This allotrope, thermodynamically stable at high pressures, is shown to be also quenchable and dynamically stable upon decompression to 1 atm, and we show its phonon dispersion curves. Present discussion includes also the relative stability of other boron allotropes as a function of pressure. We also discuss more recent publications on the putative isosymmetric phase transition in γ-B28 and the nature of chemical bonding in it. We demonstrate that a qualitative difference in the evolution of the band gap of γ-B28 and the related α-B12 structure, which is due to the partial ionicity of γ-B28.

Pressure-Induced Fm-3m R-3 Phase Transition in NaSbF6

1997 ◽  
Vol 53 (1) ◽  
pp. 25-31 ◽  
Author(s):  
H. Sowa
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
High Pressure ◽  
Sphere Packing ◽  
Low Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Pressure Phase ◽  
Type Crystal

High-pressure X-ray diffraction measurements on NaSbF6 powder were performed up to 5.63 (7) GPa. At ∼0.1 GPa the cubic low-pressure phase with ordered ReO3-type crystal structure undergoes a phase transition into a rhombohedral LiSbF6-type modification. The high-pressure behaviour of this phase is characterized by rotations and distortions of the coordination octahedra, but it also can be described with a sphere-packing deformation. The octahedral distortions are probably caused by cation–cation repulsions.

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