高压物理学报

First-Principles Study of the Isostructural Phase Transition of TiN under High Pressure

CHE Li-Xin, LI Yan, CUI Tian, ZHANG Miao, NIU Ying-Li, MA Yan-Ming, ZOU Guang-Tian

2006, 20(3): 225-229 . doi: 10.11858/gywlxb.2006.03.001

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Abstract:
The equation of state, electronic and phonon band structure of TiN under high pressures have been studied using the pseudopotential plane-wave method and linear response theory within the density functional theory. The band structure with increasing pressure indicates that there is no electronic topological transition (ETT) with pressure. There exists soft modes in the phonon spectra for TiN at ambient condition, but these soft modes don't decrease further with increasing pressure. From these results, we conclude that the experimentally observed isostructural phase transition for TiN at the pressure range of 0~12 GPa is not due to the ETT and the phonon softening.

Pressure Effect on Electrical Properties of a Manganate with Nominal Composition La1.0Ca2.0Mn2O7

ZHU Jia-Lin, LIU Zhen-Xing, YU Ri-Cheng, LI Feng-Ying, JIN Chang-Qing

2006, 20(3): 230-236 . doi: 10.11858/gywlxb.2006.03.002

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Abstract:
Pressure effects on electrical properties of a manganate with nominal composition La1.0Ca2.0Mn2O7, which has a layered perovskite structure as majority phase, have been investigated under hydrostatic pressures up to 1.05 GPa by using a self-clamped CuBe piston-cylinder cell. An abnormal pressure effect was observed. At a pressure of 0.55 GPa, a large pressure resistance effect of 40% was observed in a lower temperature range of 5~150 K. Besides, it is found that the metal-insulator transition temperature increases at low pressure but deceases with further loading pressure.

The Spectro-Studies on Micro-Mechanism of Shock Ignition for Aluminium

HU Dong, YE Song, WU Jing-He, YAN Zheng-Xin, LI Ping, SUN Zhu-Mei

2006, 20(3): 237-242 . doi: 10.11858/gywlxb.2006.03.003

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Abstract:
The aluminum powder is a high energetic material. It is added into energetic materials. The results show that the critical conditions of shock ignition for micrometer-aluminum powder relate with physical behaviour for aluminum powder. The micro-behaviour of the fast reaction for micrometer-aluminum powder are studied by means of some spectrometer techniques－three monochromaters techniques and OMA spectral techniques. The critical temperature for the micrometer-aluminum powder is about 2 100 K, and it is closed to the melting temperature of Al2O3. It is show that the Al2O3 layer must be melted, if the micrometer-aluminum powder may be ignited. It is important that the reaction of micrometer-aluminum powder with oxygen. It is not important that the reaction of micrometer-aluminum powder with water. The micrometer-aluminum powder may react, after a liquid fuel in compound fuel reacts. The reaction temperature is increased when micrometer-aluminum powder is added into energetic material and the particle size of micrometer-aluminum powder is decreased .

Experimental Research on Glass Transition Temperature of Polymers in Compressed CO2

LI Zhi-Yi, MENG Ting-Yu, LIU Xue-Wu, WANG Yi, HU Da-Peng

2006, 20(3): 243-248 . doi: 10.11858/gywlxb.2006.03.004

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Abstract:
Glass transition temperature (Tg) is an important characteristic parameter of polymers. The investigation of polymers' Tg in compressed CO2 is especially necessary for the application of supercritical fluids technique in polymer science. In this paper, based on creep compliance experimental principle, an apparatus for testing Tg of polymers in high pressure environment is established. Glass transition temperature of PET, PS, PVC and PMMA in atmosphere and in compressed CO2 has been tested. In the experiment processes, the equilibrium adsorption temperature is room temperature, and the equilibrium adsorption pressure ranges are as following: 0~3.5 MPa for PET, 0~11.0 MPa for PS, 0~9.0 MPa for PVC and 0~4.5 MPa for PMMA. The Tg obtained in atmosphere using this apparatus agree well with those in literature. This proves that the experimental method and the apparatus developed in this work are reliable and valid, so they can be applied to determine Tg of polymers at high pressure. From the results of Tg of polymers in compressed CO2, we can conclude that CO2 has distinct swelling and plasticizing effects on polymers, so that CO2 can make Tg of polymers decrease largely.

Interface Treatment Method for Multi-Component Fluids Numerical Simulation

ZHANG Xue-Ying, ZHAO Ning, WANG Chun-Wu

2006, 20(3): 249-256 . doi: 10.11858/gywlxb.2006.03.005

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Abstract:
Two interface treatment methods are applied to simulate multi-component flows. A simple and robust algorithm is provided for solving Riemann problem in 2-D. At each node of a narrow strip of the interface, Riemann problems are solved using iterative numerical method. Predicted isobaric values and ghost fluid states are provided. Comparing original GFM, this method is robust and effective. Conservative Euler equations and interface capturing equations are solved respectively. Level-set equation is applied to capture interface. Numerical computations are performed with MWENO scheme and compared with the results by -model method, original GFM and modified GFM.

Experimental Study on the Stability of Hydrous Minerals in Natural Pelitic System

LI Ying, TANG Hong-Feng, LIU Cong-Qiang, ZHOU Zhi-Hua

2006, 20(3): 257-264 . doi: 10.11858/gywlxb.2006.03.006

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Abstract:
Metamorphic dehydration of subducted sediments is of importance in understanding the composition of slab-derived fluids, the mineral and isotope composition in subduction zone, which is also important for understanding the evolution of arc magmas. The stability of chlorite, sericite, amphibole and biotite has been identified in natural pelitic system at pressures 1.5~3.5 GPa, and at temperatures 746~930 ℃ by high pressure experiments on natural pelite. The systematic diagram suggests that with the increasing of pressure and temperature chlorite completely decomposes at lower depth 50 km. The run production of this process-amphibole can be subducted to 85 km, and biotite devolatilizes at the depth 120 km in subduction zone. This leads to the conclusion that subducted sediments can be subducted into more deep depth (120 km) than basaltic oceanic crust.

Effect of Stress Anisotropy on Properties of Ferromagnetic and Antiferromagnetic Bilayer Films

RONG Jian-Hong, YUN Guo-Hong

2006, 20(3): 265-269 . doi: 10.11858/gywlxb.2006.03.007

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Abstract:
The effect of exchange anisotropy and stress anisotropy on properties of a ferromagnetic and antiferromagnetic bilayer films are investigated by ferromagnetic resonance method. It is shown that exchange anisotropy results from the unidirectional anisotropy. And stress anisotropy has large effect on hard or easy magnetization direction. When external magnetic field direction and stress field direction are parallel, the resonance frequency is shifted to higher value, and the frequency linewidth becomes wider. When external magnetic field is varied, the stress anisotropy made resonance frequency shifted to lower value. Especially, it is very complex in direction ＝ . For weak magnetic field, there are two regions. In certain magnetic field region, the resonance frequency is shifted to higher value and frequency linewidth becomes widened. However, the resonance frequency (frequency linewidth) is shifted to higher value (is widened) or lower value (is sharpened) depended on the external magnetic field in other region.

Analytical Model for Jet Formation in Shaped Charge with Wide Cone Angle

TAN Duo-Wang, SUN Cheng-Wei

2006, 20(3): 270-276 . doi: 10.11858/gywlxb.2006.03.008

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Abstract:
An analytical model for liner collapse and jet formation in shaped charge with wide cone angle is described. The basis of this model is planar detonation driving theory and PER jet formation theory. Based on this model an analytic shaped charge code (ASCC) is programmed and then used to calculated jet velocity gradient and diameter versus time for shaped charge with wide cone angle. Good agreement has been found between the experimental and the numerical results.

The Reaction of Li3N-B2O3 and Mg-B2O3 under High-Temperation and High-Pressure

SU Zuo-Peng, ZHANG Tie-Chen, DU Yong-Hui

2006, 20(3): 277-280 . doi: 10.11858/gywlxb.2006.03.009

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Abstract:
The reaction of Li3N-B2O3 and Mg-B2O3 under different pressure and temperature has been studied and the phase of the resultant has been analyzed by X-ray diffraction (XRD) method. XRD results show that when the starting material is Mg-B2O3, the major production is Mg3B2O6; When the starting material is Li3N-B2O3, cBN appears in the production. These results indicate that if the content of B2O3 is the same in the starting material, we will get different results, in the case of using Mg and Li3N as the catalyst respectively.

Olivine and Pyroxene Syntheses under High Temperature and High Pressure

DU Yong-Hui, ZHANG Tie-Chen, SU Zuo-Peng, CUI Qi-Liang

2006, 20(3): 281-284 . doi: 10.11858/gywlxb.2006.03.010

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Abstract:
Olivine (Mg2SiO4) and pyroxene (MgSiO3) single crystals were synthesized under high temperature (1 000~1 500 ℃) and high pressure (2~5 GPa) using the mixed powder of magnesium oxide (MgO) and silicon dioxide (SiO2) as starting materials. Results by TEM and XRD tests showed that the products increased with the temperature rising or the pressure decreasing. Meanwhile, phase transition relationship existed between Mg2SiO4 and MgSiO3 in this p-T ranges, and the mixed phase of Mg2SiO4-MgSiO3 would turn into the single phase of MgSiO3 at given pressure and temperature. The growth condition and character of Mg2SiO4 and MgSiO3 as well as phase transition relationship between Mg2SiO4 and MgSiO3 were discussed respectively.

Ab Initio Studies of High-Pressure Transformations in -MnO2

LI Yu-Juan, WU Xiang, QIN Shan, WU Zi-Yu

2006, 20(3): 285-290 . doi: 10.11858/gywlxb.2006.03.011

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Abstract:
First-principle calculations of MnO2 polymorphisms (rutile-type, CaCl2-type and pyrite-type) have been carried out with the full potential linearized augmented plane wave (FPLAPW) method. Through the calculations, we predict that the rutile-type MnO2 can transform to CaCl2-type at 5 GPa, and then transform to pyrite-type at 20 GPa. Furthermore, we summary the characteristic of several rutile-structure metal dioxide phases transformation under high pressure and conclude that the group Ⅳ element dioxides have similar sequence of the phase transition. In general, the pressure induced phase transformations of these group Ⅳ element dioxide take place at lower pressure with the increase of cations radii and decrease of the value of bulk moduli.

Pressure Effect on Geometric Structure of Ge R8 Phase and Its Electronic Properties

Lü Meng-Ya, CHEN Zhou-Wen, WANG Wen-Kui, LIU Ri-Ping

2006, 20(3): 291-295 . doi: 10.11858/gywlxb.2006.03.012

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Abstract:
The electronic structure of Ge R8 phase has been investigated by first-principles method based on plane-wave basis, using norm-conserving pseudopotential and local density approximation. The dependence of structural parameters including lattice constants, rhombohedral angle, and atomic coordinates on pressure was also studied. The computed energy band-structure indicates that Ge R8 phase is a semimetal. Analysis of the total density of states and partial density of states shows a sharpening of valence-band edge, and the distribution of orbits was considered. At the same time, the variation of two different bond lengths was given along pressure which decreases with the increase of pressure; the underlying mechanism is also discussed.

Experimental Measurement for Shock Temperature of Liquid Argon up to 33 GPa

MENG Chuan-Min, SHI Shang-Chun, HUANG Hai-Jun, JI Guang-Fu, TANG Jing-You, YANG Xiang-Dong

2006, 20(3): 296-300 . doi: 10.11858/gywlxb.2006.03.013

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Abstract:
Shock temperature of liquid argon has been measured under the shock pressure up to 33 GPa by employing the two-stage light gas gun. Impactor velocities were measured with electrical-magnetic induction system. Shock velocities and shock temperature of liquid argon were measured by using optical-fiber pyrometer. Mass velocities were obtained by mean of shock impendence matching method. The experimental data shows that shock temperature reach 10 000 K at 33 GPa shock pressure. Over 30 GPa shock pressure, shock temperature is lower compared with theoretical data. The experimental data also shows that the slope of shock temperature-shock volume curve begins to decrease over 30 GPa, which is the same shock pressure as the previously published shock Hugoniot curve.

Discussion on the Improvement of the Dn() Relation of IHE

ZHAO Ji-Bo, ZHAO Feng, TAN Duo-Wang, ZHANG Guang-Sheng, PU Zheng-Mei, SUN Yong-Qiang

2006, 20(3): 301-307 . doi: 10.11858/gywlxb.2006.03.014

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Abstract:
The phase velocity and wave shape of insensitive high explosive with diverse diameter were measured. Through analyses of those data, the relation of Dn and is discussed. With the same curve, the greater of the ratio of curve, the faster the reduction of normal velocity is. So the Dn() is used in whole wave shape. The calculated result used by LS method with the new relation is in agreement well with the experimental data.

Equation of State for Gold

ZOU Yong, CHEN Li-Rong

2006, 20(3): 308-312 . doi: 10.11858/gywlxb.2006.03.015

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Abstract:
A modified calculative formula for the thermal pressure is proposed and the equation of state (EOS) is obtained accordingly for gold. We compared this EOS with the other two common EOS using the experimental data for gold. The results show that the new EOS is better than the other two EOS at high temperature.

Comparative Research of Applicability of Four Isothermal Equations of State

HU Jing, SUN Jiu-Xun, CAI Ling-Cang

2006, 20(3): 313-321 . doi: 10.11858/gywlxb.2006.03.016

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Abstract:
It is pointed out that four equations of state are popular in literature, including Morse, Vinet, Born-Meyer (BM) and Baonza equations of state. The four equations have been applied to fit the experimental compression data of 50 materials. The optimized values of bulk modulus and its first-order pressure derivative at zero-pressure have been determined, and the average errors are compared. The results show that for all materials the Morse equation gives the best results with average error 0.557 6%, BM, Vinet and Baonza equations subsequently give inferior results with average errors 0.615 1%, 0.788 9% and 0.833 3%, respectively. For materials at wide pressure range, we recommend the Morse equation, but at middle and low pressure ranges, we recommend the Baonza equation as it can be expressed as both pressure analytic form and volume analytic form.

The Grounding Problem in the Measurement with Manganin Pressure Gauge

WANG Wei, WANG Xiang, YE Su-Hua

2006, 20(3): 322-326 . doi: 10.11858/gywlxb.2006.03.017

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Abstract:
The manganin pressure gauge is one of the most used sensors in shock wave physics experiments. The grounding problem for the measurement of shock pressure by manganin gauge is stated and discussed in this paper. The analysis and experiments show that the incorrect grounding methods will bring large error in the measurement of shock pressure or even abnormal profiles.

A on-Line Program to Process Laser Equation of State Experimental Data

SHU Hua, FU Si-Zu, HUANG Xiu-Guang, MA Min-Xun, GU Yuan

2006, 20(3): 327-330 . doi: 10.11858/gywlxb.2006.03.018

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Abstract:
A on-line program which can process laser equation of state experimental data more effectively has been developed. The processing program can decrease random error due to manual process, and it can process data much more effectively and process experimental data on-line.

Design of the Sample Assembly for Ultrasonic Measurement at High Pressure and 300 K in Six-Side Anvil Cell

WANG Qing-Song, WANG Zhi-Gang, BI Yan

2006, 20(3): 331-336 . doi: 10.11858/gywlxb.2006.03.019

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Abstract:
We introduced briefly the principle of design of sample assembly for ultrasonic measurements at high pressure, and designed a new kind of sample assembly to measure the isothermal compression of Al and Cu at 300 K. Ideal quasi-hydrostatic loading was realized, and high-quality ultrasonic signals were obtained under high pressure. It was indicated that the design of sample assembly was reasonable. We analyzed in brief main uncertainty of ultrasonic measurement in six-side anvil cell at 300 K.

2006 Vol. 20, No. 3

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