scholarly journals STRUCTURAL PHASE STABILITY IN GROUP IV METALS UNDER STATIC HIGH PRESSURE

2009 ◽  
Author(s):  
N. Velisavljevic ◽  
G. N. Chesnut ◽  
D. M. Dattelbaum ◽  
Y. K. Vohra ◽  
A. Stemshorn ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Stability ◽  
Structural Phase ◽  
Group Iv ◽  
Group Iv Metals

scholarly journals Pressure-Induced Structural Phase Transition and Metallization in Ga2Se3 up to 40.2 GPa under Non-Hydrostatic and Hydrostatic Environments

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 746
Author(s):  
Meiling Hong ◽  
Lidong Dai ◽  
Haiying Hu ◽  
Xinyu Zhang
Keyword(s):  
Phase Transition ◽  
Electrical Conductivity ◽  
High Pressure ◽  
Phase Transformation ◽  
Transport Properties ◽  
Electrical Transport ◽  
Structural Phase ◽  
Structure Evolution ◽  
Systematic Research ◽  
Electrical Transport Properties

A series of investigations on the structural, vibrational, and electrical transport characterizations for Ga2Se3 were conducted up to 40.2 GPa under different hydrostatic environments by virtue of Raman scattering, electrical conductivity, high-resolution transmission electron microscopy, and atomic force microscopy. Upon compression, Ga2Se3 underwent a phase transformation from the zinc-blende to NaCl-type structure at 10.6 GPa under non-hydrostatic conditions, which was manifested by the disappearance of an A mode and the noticeable discontinuities in the pressure-dependent Raman full width at half maximum (FWHMs) and electrical conductivity. Further increasing the pressure to 18.8 GPa, the semiconductor-to-metal phase transition occurred in Ga2Se3, which was evidenced by the high-pressure variable-temperature electrical conductivity measurements. However, the higher structural transition pressure point of 13.2 GPa was detected for Ga2Se3 under hydrostatic conditions, which was possibly related to the protective influence of the pressure medium. Upon decompression, the phase transformation and metallization were found to be reversible but existed in the large pressure hysteresis effect under different hydrostatic environments. Systematic research on the high-pressure structural and electrical transport properties for Ga2Se3 would be helpful to further explore the crystal structure evolution and electrical transport properties for other A2B3-type compounds.

Correct Structural Phase Stability of FeS2, TiO2, and MnO2 from a Semilocal Density Functional

2021 ◽  
Vol 125 (7) ◽  
pp. 4284-4291
Author(s):  
Bikash Patra ◽  
Subrata Jana ◽  
Lucian A. Constantin ◽  
Prasanjit Samal
Keyword(s):  
Phase Stability ◽  
Density Functional ◽  
Structural Phase

High-pressure structural phase transition and metallization in Ga2S3 under non-hydrostatic and hydrostatic conditions up to 36.4 GPa

2021 ◽  
Author(s):  
Linfei Yang ◽  
Jianjun Jiang ◽  
Lidong Dai ◽  
Haiying Hu ◽  
Meiling Hong ◽  
...  
Keyword(s):  
Phase Transition ◽  
Raman Spectroscopy ◽  
High Pressure ◽  
Structural Properties ◽  
Structural Phase Transition ◽  
First Principles ◽  
Theoretical Calculations ◽  
Structural Phase

The vibrational, electrical and structural properties of Ga2S3 were explored by Raman spectroscopy, EC measurements, HRTEM and First-principles theoretical calculations under different pressure environments up to 36.4 GPa.

scholarly journals Phase Stability of Iron Nitride Fe4N at High Pressure—Pressure-Dependent Evolution of Phase Equilibria in the Fe–N System

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3963
Author(s):  
Marius Holger Wetzel ◽  
Tina Trixy Rabending ◽  
Martin Friák ◽  
Monika Všianská ◽  
Mojmír Šob ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Equilibria ◽  
Phase Stability ◽  
Polymorphic Transition ◽  
Ex Situ ◽  
Stable Phase ◽  
Iron Nitride ◽  
Phase System ◽  
Target Composition ◽  
Heat Treated

Although the general instability of the iron nitride γ′-Fe4N with respect to other phases at high pressure is well established, the actual type of phase transitions and equilibrium conditions of their occurrence are, as of yet, poorly investigated. In the present study, samples of γ′-Fe4N and mixtures of α Fe and γ′-Fe4N powders have been heat-treated at temperatures between 250 and 1000 °C and pressures between 2 and 8 GPa in a multi-anvil press, in order to investigate phase equilibria involving the γ′ phase. Samples heat-treated at high-pressure conditions, were quenched, subsequently decompressed, and then analysed ex situ. Microstructure analysis is used to derive implications on the phase transformations during the heat treatments. Further, it is confirmed that the Fe–N phases in the target composition range are quenchable. Thus, phase proportions and chemical composition of the phases, determined from ex situ X-ray diffraction data, allowed conclusions about the phase equilibria at high-pressure conditions. Further, evidence for the low-temperature eutectoid decomposition γ′→α+ε′ is presented for the first time. From the observed equilibria, a P–T projection of the univariant equilibria in the Fe-rich portion of the Fe–N system is derived, which features a quadruple point at 5 GPa and 375 °C, above which γ′-Fe4N is thermodynamically unstable. The experimental work is supplemented by ab initio calculations in order to discuss the relative phase stability and energy landscape in the Fe–N system, from the ground state to conditions accessible in the multi-anvil experiments. It is concluded that γ′-Fe4N, which is unstable with respect to other phases at 0 K (at any pressure), has to be entropically stabilised in order to occur as stable phase system. In view of the frequently reported metastable retention of the γ′ phase during room temperature compression experiments, energetic and kinetic aspects of the polymorphic transition γ′⇌ε′ are discussed.

The structural phase transition of ammonia borane under high pressure

2020 ◽  
Vol 45 (58) ◽  
pp. 33047-33058
Author(s):  
Lan-Ting Shi ◽  
Cui-E Hu ◽  
Alfonso Muñoz ◽  
Lin-Xiang Ji ◽  
Yao-Yao Huang ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Ammonia Borane
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