高压物理学报

Effect of High Pressure on Electronic Structure of Super conducting La1.85Sr0.15CuO4

HAO Xue-Jun, ZHANG Li-Yuan, WANG Huai-Yu

1994, 8(1): 1-8 . doi: 10.11858/gywlxb.1994.01.001

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Abstract:
The electronic structure of La1.85Sr0.15CuO4 under atmosphere, 1 GPa, 4 GPa, 8 GPa has been calculated by the Recursion method. The changes of Fermi energy, total density dstates at EF, atomic valence at each site are given. Our results show that the change of Tc under high pressure is not due to the change of EF or N(EF), but may be caused by the variation of hole number of Cu and O2 on the CuO2 plane. The rise Of O2 p holes is favorable for superconductivity in this system.

Problem of Heat Conduction behind a Shock Wave Front

ZHANG Guan-Ren

1994, 8(1): 9-13 . doi: 10.11858/gywlxb.1994.01.002

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Abstract:
In this paper, the author proves that there exists a heat conduction wave behind a shock front. If the radiation is not considered, the speed of the heat wave exactly coincides with that of the shock wave, but it has its own distribution behind the shock front.

Some Topics in Shock-Induced Phase Transitions

TANG Zhi-Ping

1994, 8(1): 14-22 . doi: 10.11858/gywlxb.1994.01.003

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Abstract:
In this paper, the progresses and trends in some active topics for shock-induced phase transition research are reviewed, such as phase transition plasticity, shear stress effects, post-phase-transition behavior, theory and constitutive description for shock-induced phase transitions, and instantaneous and real-time measurements for microscopic mechanisms. The importance for direct measurement of transverse shear behavior of materials under shock loading is emphasized.

Experimental Studies of the Blowoff Impulses Produced in the Flat Plate Targets Bombarded by Electron Beam

PENG Chang-Xian, XU Yong-Liang, XU Jian-Bo

1994, 8(1): 23-29 . doi: 10.11858/gywlxb.1994.01.004

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Abstract:
The blowoff impulses are the condition of applied loads of the structural response induced in the target structures bombarded by electron beam. In this paper, the experimental studies of the blowoff impulses produced in the flat plate targets bombarded by electron beam on FLASH-Ⅱ equipment of late years are discussed. In experiments, the eddy transducers and the probe principle of directly measuring the specific time intervals were used. The used target materials are LY-12 aluminum alloy and glass fiber reinforced plastic. The range of the energy fluxes on targets is 70～100 J/cm2. The range of the measured impulses is 150～210 Pa#8226;s. The measured coupling coefficients of impulses are stable basically. Their values equal to about 2.06 Pas/(J/cm2).

Hydrostatic Pressure Dependence of Forced Volume Magnetostriction of Seven Amorphous Alloys

SU Fang, SU Jun

1994, 8(1): 30-35 . doi: 10.11858/gywlxb.1994.01.005

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Abstract:
Forced volume magnetostriction is too minute 10-10~10-9[(103/4)(A/m)]-1 to be measured accurately by repeated addition of linear magnetostriction 10-6[(103/4)(A/m)]-1. According to thermodynamic relation, (d/dH)T,p=-(dMs/dp)T,H ,we measured the Ms-p curve and obtained the hydrostatic pressure dependence of forced volume magnetostriction of seven amorphous alloys－Fe81.6Si4.6B13.8, Fe46.3Co0.03Ni46.5Si3.75V0.92B2.5, Fe75Cr5Si5B15, Fe73.9Co8.3Si4.4B13.4, Fe75Ni5Si5B15, Fe78.75Cu1.25Si5B15 and (Fe0.85Co0.15)82Cu0.4Si4.4B13.2 in the range from 0.000 1 to 2.4 GPa. The results show clearly two kinds. (1) Six of them belong to the first type of pressure effect on magnetism. (d/dH)T,p is positive under most of pressure, i. e. Ms diminishes when p increases. (d/dH)T,p is negative only in some narrow ranges of pressure. It is due to variation of chemical short range order which is composed of magnetic atoms and non-magnetic atoms under different pressure. (2) Amorphous alloy Fe78.75Cu1.25Si5B15 belongs to the second type of pressure effect on magnetism. (d/dH)T,p is negative under most of pressure. Anomalous rise of Ms is related to the special role of Cu.

Thick-Grain Diamonds Growth and Ascertainment of Its Thermodynamic Conditions

LIN Ming-Xi, LI Ying-Hua

1994, 8(1): 36-42 . doi: 10.11858/gywlxb.1994.01.006

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Abstract:
In this paper, starting from theory of thermodynamics, we have studied the dispersion characteristic of crystalline-grain and crystalline-quality of diamonds, on the basis of equilibrium diagram theory of graphite-diamond (G-D) phases. The key to the discussion is placed on the growth districts of thick-grain-size diamond and their thermodynamic conditions. Guided by the above-mention theory, we got good results in our productive test.

A Method for Indirect Observation of the Pressure in the Cylindrical Metal Tube under Shock Compression

HUA Jin-Song, DONG Qing-Dong, TAN Hua

1994, 8(1): 43-48 . doi: 10.11858/gywlxb.1994.01.007

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Abstract:
The paper describes a method to observe the pressure of powder samples filled in a cylindrical metal tube which will be subjected to explosive compression. As an example, we measured the pressure in the explosive shock synthesis of wurtzite-type boron nitride (wBN) from graphite-type BN. The results show that the shock pressure in the sample tube ranges from about 11.5 GPa to 22 GPa (which satisfies the pressure condition required by the shock synthesis of wBN) and that the pressure in the tube varies discontinuously. These experimental results indicate that this technique is feasible.

A Theoretical Study on Heat Conduction Following Shock Compression

LIN Hua-Ling, YU Wan-Rui

1994, 8(1): 49-56 . doi: 10.11858/gywlxb.1994.01.008

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Abstract:
The interface temperature and the temperature history near the interface following the shock compression are calculated by the method of Cattaneo heat conduction. They are compared with the results via Fourier heat conduction. The effects of thermal relaxation time constants on the interface temperatures, and so on, are analyzed.

Electronic Structure and EOS of -SiC

XIE Yuan-Nan

1994, 8(1): 57-59 . doi: 10.11858/gywlxb.1994.01.009

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Abstract:
By using LMTO-ASA method, the computational results including electronic structure and EOS of covalent crystal -SiC are presented. The compressibility ranges from 1.0 to 2.5. We put two empty spheres into WS sell to simulate compact-packed situation. It is shown that the used method is adapted for loose-packed crystal.

Influence of High Pressure on Formation of Intermediate Phases of Mn4Si and Formation of Dodacagonal Quasicrystal in Mn4Si Alloy under High Static Pressure

XU Da-Peng, SONG Yan-Bin, SU Wen-Hui, LIN Hua-Mao

1994, 8(1): 60-64 . doi: 10.11858/gywlxb.1994.01.010

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Abstract:
The formation and stability of the intermediate phases of Mn4Si have been investigated by the method of quenching in fusing state under high static pressure (MQFSHP). The results show that (Mn4Si) phase , which is the main part in the Mn4Si alloy smelted in vacuum furnace is unstable; (Mn4Si) R phase, which is not in the Mn4Si alloy smelted in vacuum, is observed by quenching from fusing state under high pressure. The dodecagonal quasicrystal has been found in Mn4Si system by MQFSHP for the first time. The structure and stability of intermediate phases and dodecagonal quasicrystal were analyzed by using X-ray diffraction, electron diffraction and DTA techniques.

Synthesis of High-Pressure Diamond Using Graphite Over Which CVD Diamond Grains Were Grown

JIN Zeng-Sun, Lü Xian-Yi, ZHANG Tie-Chen, ZOU Guang-Tian

1994, 8(1): 65-68 . doi: 10.11858/gywlxb.1994.01.011

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Abstract:
CVD diamond grains have been grown on polycrystalline graphite pieces by the hot-filament CVD method using mixtures of methane and hydrogen, and high-pressure diamond was synthesized by 66 MN (6600 t) cubic high pressure apparatus using CVD diamond-grown graphite. The experimental results show that growth features of CVD diamond on the polycrystalline graphite substrate depended largely on the total pressure when other conditions were same, growth of CVD diamond grains on the graphite pieces used as starting material is a possible way of increasing transformation rate of graphite to diamond and of lowering the synthesis pressure at the synthesis of high-pressure diamond.

X-Ray Diffraction Experiment Observation of Ag at over 100 GPa Pressrues

GU Hui-Cheng, LI Feng-Ying, WANG Ji-Fang, CHEN Liang-Chen

1994, 8(1): 69-72 . doi: 10.11858/gywlxb.1994.01.012

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Abstract:
In this paper, the experimental methods and procedures at over 100 GPa pressure were described in detail. The experiments were carried out in a high pressure device with lever type diamond anvil cell (DAC). An in situ over 100 GPa high pressure X-ray diffraction observation of Ag was conducted at a pressure up to 121 GPa, some significant experimental curves and results were obtained.

Pressure-Induced Formation of Amorphous Alloys

LI Dong-Jian, WANG Jing-Tang, DING Bing-Zhe, LI Shu-Ling

1994, 8(1): 73-79 . doi: 10.11858/gywlxb.1994.01.013

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Abstract:
The high pressure amorphization is studied in this paper, and the influence of pressure was discussed on the nucleation free energy, critical cooling rate during quenching process. Theoretical analyses indicate that the formation of metastable phase (MP) is the prerequisite of that of amorphous phase, and the MP can form only in the system which volume phase transitions expanded during cooling. For these systems, pressure can accelerate nucleation, restrain diffusion, and decrease the critical cooling rate, which results in the formation of MP. There exists a critical pressure, and MP is only formed when pressure is over the critical one. In the end, the MP transforms into amorphous phase as a result of the limitation of dynamic conditions.

1994 Vol. 8, No. 1

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