scholarly journals Pressure-induced phase transition of 1,5-diamino-1H-tetrazole (DAT) under high pressure

RSC Advances ◽  
2020 ◽  
Vol 10 (50) ◽  
pp. 30069-30076
Author(s):  
Cheng Jin ◽  
Ying Liu ◽  
Lijuan Wang ◽  
Weijing Zhang ◽  
Tonglai Zhang ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Phase Transitions

DAT experiences phase transitions under pressure related to rotation of NH2 and distortion of the heterocycle.

scholarly journals Viscosity Measurement of Olive Oil under Pressure

2021 ◽  
Vol 6 (5) ◽  
Author(s):  
Pawlicki LT
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Phase Transitions ◽  
Liquid Phase ◽  
Olive Oil ◽  
Measurement Method ◽  
Viscosity Measurement ◽  
Food Preservation ◽  
Characteristic Frequencies ◽  
Viscosity Changes

This article presents changes in the viscosity of olive oil during compression. The test was carried out indirectly by measuring the dependence of the resonance frequency of the piezoelectric immersed in olive oil on pressure. For this purpose, for successive pressures, the resonance curves were read and the values of the characteristic frequencies were determined. Viscosity changes were analysed and related to the compression and crystallization taking place in the tested substance. During this research, a phase transition from the liquid phase to the alpha crystalline phase was detected, during which the resonant frequency of the tested piezoelectric reached a minimum and the viscosity related to this frequency reached a maximum. The measurement method developed in this paper can be used to detect the phase transitions of oils subjected to pressure. This may find application in the oil production and high-pressure food preservation industries for which this knowledge is essential for the safe and trouble-free use of their machines.

scholarly journals Phase transitions and critical phenomena of ice under high pressure

2014 ◽  
Vol 70 (a1) ◽  
pp. C894-C894
Author(s):  
Masakazu Matsumoto ◽  
Kazuhiro Himoto ◽  
Kenji Mochizuki ◽  
Hideki Tanaka
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Phase Transitions ◽  
Phase Boundary ◽  
Liquid Water ◽  
Tricritical Point ◽  
Melting Curve ◽  
Md Simulations ◽  
Free Energy Calculations ◽  
Lattice Points

Water distributes ubiquitously among the solar system and outer space in a wide variety of solid forms, i.e. more than ten kinds of crystalline ice, two types of amorphous ice, and clathrate hydrates. These polymorphs often play crucial roles in the planetary geology. Diversity of the stable ices and hydrates also suggests the existence of the various kinds of stable and metastable phases yet to be discovered [1]. Computer simulations and the theoretical treatments are useful to explore them. In this talk, we introduce the phase transitions of ice VII, which is one of the highest-pressure ice phases. The melting curve of ice VII to high-pressure liquid water has not been settled by experiments. We have proposed the intervention of a plastic phase of ice (plastic ice) between ice VII and liquid water, based on molecular dynamics (MD) simulations and the free energy calculations [2], which enables to account for large gaps among the various experimental curves of ice VII. In plastic ice, the water molecules are fixed at the lattice points, while they rotate freely. Interestingly, our additional survey by large-scale MD simulations elucidates that the phase transition between ice VII and plastic ice is first-order at low pressure as it was already predicted, while it is found to be second-order at higher pressures, where a tricritical point joins these phase boundaries together [3]. The critical fluctuations may give a clue for determining the phase boundary experimentally. We also argue about the phase transition dynamics of liquid water to ice VII at their direct phase boundary where metastable plastic ice phase plays an important role.

Phase transitions of BaCO3 at high pressures

2008 ◽  
Vol 72 (2) ◽  
pp. 659-665 ◽  
Author(s):  
S. Ono ◽  
J. P. Brodholt ◽  
G. D. Price
Keyword(s):  
Phase Transition ◽  
Experimental Study ◽  
High Pressure ◽  
Phase Transitions ◽  
Bulk Modulus ◽  
First Principles ◽  
High Pressures ◽  
Ambient Conditions ◽  
The Stability ◽  
Previous Experimental Study

AbstractFirst-principles simulations and high-pressure experiments were used to study the stability of BaCO3 carbonates at high pressures. Witherite, which is orthorhombic and isotypic with CaCO3 aragonite, is stable at ambient conditions. As pressure increases, BaCO3 transforms from witherite to an orthorhombic post-aragonite structure at 8 GPa. The calculated bulk modulus of the post-aragonite structure is 60.7 GPa, which is slightly less than that from experiments. This structure shows an axial anisotropicc ompressibility and the a axis intersects with the c axis at 70 GPa, which implies that the pressure-induced phase transition reported in previous experimental study is misidentified. Although a pyroxene-like structure is stable in Mg- and Ca-carbonates at pressures >100 GPa, our simulations showed that this structure does not appear in BaCO3.

Phase Transition Behavior of Solids under Shock Compression

2010 ◽  
Vol 638-642 ◽  
pp. 1053-1058 ◽  
Author(s):  
Tsutomu Mashimo
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Phase Transitions ◽  
Equations Of State ◽  
Relaxation Times ◽  
Inorganic Materials ◽  
High Pressure Phase ◽  
High Time Resolution ◽  
Compression Process ◽  
Pressure Phase

Through the measurement of Hugoniot parameters, we can get useful information about high-pressure phase transitions, equations of state (EOS), etc. of solids, without pressure calibration. And, we can discuss the transition dynamics, because the relaxation times of phase transition and compression process are of the same order. We have performed the Hugoniot-measurement experiments on various kinds of compound materials including oxides, nitrides, borides and chalcogenides by using a high time-resolution streak photographic system combined with the propellant guns. The structure-phase transitions have been observed for several kinds of inorganic materials, TiO2, ZrO2, Gd3Ga5O12, AlN, ZnS, ZnSe, etc. The phase transition pressures under shock and static compressions of metals, ionic materials, semiconductors and some ceramics are consistent with each other. Those are not consistent for strong covalent bonding materials such as C, BN and SiO2. Here, the Hugoniot compression data are reviewed, and the shock-induced phase transitions and the dynamics are discussed, as well as the EOS of the high-pressure phase up to evem 1 TPa.

scholarly journals X-Ray Diffraction and Electron Microscopy Studies of the Size Effects on Pressure-Induced Phase Transitions in CdS Nanocrystals

MRS Advances ◽  
2020 ◽  
pp. 1-9
Author(s):  
Lingyao Meng ◽  
Hongyou Fan ◽  
J. Matthew Lane ◽  
Luke Baca ◽  
Jackie Tafoya ◽  
...  
Keyword(s):  
Phase Transition ◽  
Particle Size ◽  
High Pressure ◽  
Phase Transitions ◽  
Size Effects ◽  
High Pressures ◽  
Bulk Material ◽  
Cds Nanoparticles ◽  
X Ray ◽  
Potential Applications

Abstract In recent years, investigations of the phase transition behavior of semiconducting nanoparticles under high pressure has attracted increasing attention due to their potential applications in sensors, electronics, and optics. However, current understanding of how the size of nanoparticles influences this pressure-dependent property is somewhat lacking. In particular, phase behaviors of semiconducting CdS nanoparticles under high pressure have not been extensively reported. Therefore, in this work, CdS nanoparticles of different sizes are used as a model system to investigate particle size effects on high-pressure-induced phase transition behaviors. In particular, 7.5, 10.6, and 39.7 nm spherical CdS nanoparticles are synthesized and subjected to controlled high pressures up to 15 GPa in a diamond anvil cell. Analysis of all three nanoparticles using in-situ synchrotron wide-angle X-ray scattering (WAXS) data shows that phase transitions from wurtzite to rocksalt occur at higher pressures than for bulk material. Bulk modulus calculations not only show that the wurtzite CdS nanomaterial is more compressible than rocksalt, but also that the compressibility of CdS nanoparticles depends on their particle size. Furthermore, sintering of spherical nanoparticles into nanorods was observed for the 7.5 nm CdS nanoparticles. Our results provide new insights into the fundamental properties of nanoparticles under high pressure that will inform designs of new nanomaterial structures for emerging applications.

The Theoretical Study of the Cinnabar-to-Rocksalt Phase Transitions of HgTe and CdTe under High Pressure

2014 ◽  
Vol 1004-1005 ◽  
pp. 1608-1614 ◽  
Author(s):  
Xi Duo Hu ◽  
De Hai Zhu ◽  
Zhi Feng Zeng ◽  
Shao Rui Sun
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Phase Transitions ◽  
Theoretical Study ◽  
Chain Structure ◽  
Two Phase ◽  
Principle Calculation ◽  
First Principle Calculation ◽  
First Order ◽  
Rocksalt Phase

We performed the first-principle calculation to study the structures of cinnabar phase and the Cinnabar-to-rocksalt Phase transitions of HgTe and CdTe under high pressure. The calculated results show that for HgTe, the zincblende-to-cinnabar phase transition is under 2.2GPa, and the cinnabar-to-rocksalt phase transition is under 5.5 GPa; For CdTe, the two phase transitions occur under 4.0 GPa and 4.9 GPa, respectively, which well agree with the experimental results. The cinnabar-to-rocksalt phase transitions of most compounds, including HgTe and CdTe, except HgS are of first-order, and it is due to that their cinnabar phases are not chain structure as HgS and there are no relaxation process before the phase transition.

High-pressure phase transitions in the rare-earth orthoferrite LaFeO3

2014 ◽  
Vol 70 (3) ◽  
pp. 452-458 ◽  
Author(s):  
Martin Etter ◽  
Melanie Müller ◽  
Michael Hanfland ◽  
Robert E. Dinnebier
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Phase Transitions ◽  
Equations Of State ◽  
Spin Transition ◽  
Structural Phase ◽  
Two Phase ◽  
Pressure Derivative ◽  
Temperature Isotherm ◽  
Hydrostatic Limit

Sequential Rietveld refinements were applied on high-pressure synchrotron powder X-ray diffraction measurements of lanthanum ferrite (LaFeO3) revealing two phase transitions on the room-temperature isotherm up to a pressure of 48 GPa. The first structural phase transition of second order occurs at a pressure of 21.1 GPa, changing the space group fromPbnmtoIbmm. The second transition, involving a isostructural first-order phase transition, occurs at approximately 38 GPa, indicating a high-spin to low-spin transition of the Fe3+ion. Following the behavior of the volume up to the hydrostatic limit of methanol–ethanol it was possible to use inverted equations of state (EoS) to determine a bulk modulus ofB0= 172 GPa and a corresponding pressure derivative ofB′0= 4.3. In addition, the linearized version of the inverted EoS were used to determine the corresponding moduli and pressure derivatives for each lattice direction.

PHASE TRANSITION AND THERMODYNAMIC PROPERTIES OF MAGNESIUM FLUORIDE BY FIRST PRINCIPLES

2014 ◽  
Vol 28 (08) ◽  
pp. 1450026 ◽  
Author(s):  
TIAN ZHANG ◽  
YAN CHENG ◽  
ZHEN-LONG LV ◽  
GUANG-FU JI ◽  
MIN GONG
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Phase Transitions ◽  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
Structural Phase ◽  
Harmonic Approximation ◽  
Electronic Density ◽  
Good Agreement

The structural stabilities, phase transitions and thermodynamic properties of MgF 2 under high pressure and temperature are investigated by first-principles calculations based on plane-wave pseudopotential density functional theory method within the local density approximation. The calculated lattice parameters of MgF 2 in all four phases under zero pressure and zero temperature are in good agreement with the existing experimental data and other theoretical results. Our results demonstrate that MgF 2 undergoes a series of structural phase transitions from rutile (P42/mnm)→ CaCl 2-type (Pnnm)→ modified fluorite (Pa-3)→ cotunnite (Pnam) under high pressure and the obtained transition pressures are in fairly good agreement with the experimental results. The temperature-dependent volume and thermodynamic properties of MgF 2 in the rutile phase at 0 GPa are presented and the thermodynamic properties of MgF 2 in the rutile, CaCl 2-type, modified fluorite and cotunnite phases at 300 K are also predicted using the quasi-harmonic approximation model (QHA) and the quasi-harmonic Debye model (QHD), respectively. Moreover, the partial density of states and the electronic density of the four phases under the phase transition are also investigated.

Phase Transition and ThermodynamicProperties of OsN2 under High Pressure

2013 ◽  
Vol 401-403 ◽  
pp. 660-662
Author(s):  
Zhi Jian Fu ◽  
Li Jun Jia ◽  
Wei Long Quan
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Thermal Expansion ◽  
Phase Transitions ◽  
Transition Temperature ◽  
Thermodynamic Properties ◽  
First Principles ◽  
Fluorite Structure ◽  
First Principles Calculations ◽  
Zero Temperature

The lattice parameters, phase transition, and thermodynamic properties of OsN2in pyrite and fluorite structure are investigated by first-principles calculations. The pressure and temperature induced phase transitions of OsN2from fluorite structure to pyrite structure have been obtained. It is found that the transition pressure of OsN2at zero temperature is 158.2 GPa, and there exists no transition temperature. In addition, the thermal expansion, the Debye temperature, and the Grüneisen parameter in diverse pressures and temperatures about these two structures have also been obtained. Key words: transition phase; thermodynamic properties; OsN2PACS numbers: 71.15.Mb, 64.70.Kb

Raman Spectroscopic Studies of the Phase Transitions in Hexane at High Pressure

2005 ◽  
Vol 59 (12) ◽  
pp. 1498-1500 ◽  
Author(s):  
Wang Huai ◽  
Zheng Haifei ◽  
Sun Qiang
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Phase Transitions ◽  
Spectroscopic Study ◽  
Spectroscopic Studies ◽  
Frequency Bandwidth ◽  
Cubic Zirconia ◽  
Raman Spectroscopic ◽  
Raman Spectroscopic Study

Raman spectroscopic study of n-hexane was carried out in a cubic zirconia anvil cell up to approximately 2.0 GPa. Under high pressure, the C–H stretching region of the spectrum at 2850–3000 cm−1 shows measurable changes in frequency, bandwidth, and intensity. These Raman bands shift towards higher frequencies with increasing pressure. At about 1.4 GPa, phase transition from liquid to solid was induced by compression, as was simultaneously observed with the built-in microscope.

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