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In-Situ Conductivity Measurement of BaF2 under High Pressure and High Temperature

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Chinese Physics Letters 2006年第11期23卷 2917-2919页

作者：郝爱民高春晓李明贺春元黄晓伟张东梅于翠玲邹广田李延春李晓东刘景 State Key Laboratory for Superhard Materials Jilin University Changchun 130012 Department of Mathematics and Physics Hebei Normal University of Science and Technology Qinhuangdao 066004 Beijing Synchrotron Radiation Facility Chinese Academy of Sciences Beijing 100039

We perform the in-situ conductivity measurement on BaF2 at high pressure using a microcircuit fabricated on a diamond anvil cell. The results show that BaF2 initially exhibits the electrical property of an insulator at pressure below 25 GPa, it transforms to a wide energy gap semiconductor at pressure from 25 to 30 GPa, and the conductivity increases gradually with increasing pressure from 30 GPa. However, the metallization predicted by theoretical calculation at 30-33 GPa cannot be observed. In addition, we measure the temperature dependence of the conductivity at several pressures and obtain the relationship between the energy gap and pressure. Based on the experimental data, it is predicted that BaF2 would transform to a metal at about 87 GPa and ambient temperature. The conductivity of BaF2 reaches the order of 10^-3Ω^-1 cm^-1 at 37 GPa and 2400 K, the superionic conduction is not observed during the experiments, indicating the application of pressure elevates greatly the transition temperature of the superionic conduction.

关键词： DIAMOND-ANVIL CELL ELASTIC-CONSTANTS phase-transitions IONIC-CONDUCTIVITY CRYSTALS FLUORIDE SIMULATIONS DEPENDENCE RESISTANCE SRCL2

Fractional Fourier Transform of Cantor Sets

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Chinese Physics Letters 2005年第9期22卷 2316-2319页

作者：廖天河高穹 Department of Physics Information Engineering University Zhengzhou 450001

A new kind of multifractal is constructed by fractional Fourier transform of Cantor sets. The wavelet transform modulus maxima method is applied to calculate the singularity spectrum under an operational definition of multifractal. In particular, an analysing procedure to determine the spectrum is suggested for practice. Nonanalyticities of singularity spectra or phase transitions are discovered, which are interpreted as some indications on the range of Boltzmann temperature q, on which the scaling relation of partition function holds.

关键词： DIFFUSION-LIMITED AGGREGATION phase-transitions THERMODYNAMICFORMALISM OPTICAL IMPLEMENTATION STRANGE SETS MULTIFRACTALS DIMENSION FRACTALS

Finite-Size Scaling Analysis of a Three-Dimensional Blume-Capel Model in the Presence of External Magnetic Field

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Chinese Physics Letters 2008年第7期25卷 2599-2602页

作者： H. Demirel A. Ozkan B. Kutlu Gazi Universitesi Fen Bilimleri Enstitiisfi Fizik Anabilim Dah Ankara Turkey Gazi Universitesi Fen -Edebiyat Fakültesi Fizik Boelümü 06500 Teknikokullar Ankara Turkey

The Blume-Capel model in the presence of external magnetic field H has been simulated using a cellular automaton algorithm improved from the Creutz cellular automaton in three-dimension lattice. The field critical exponent 5 is estimated using the power law relations and the finite size scaling functions for the magnetization and the susceptibility in the range -0.1≤ h = H/J ≤0. The estimated value of the field critical exponent 5 is in good agreement with the universal value （δ = 5） in three dimensions. The simulations are carried out on a simple cubic lattice under periodic boundary conditions.

关键词： 2-DIMENSIONAL ISING-MODEL CREUTZ CELLULAR-AUTOMATON EMERY-GRIFFITHS MODEL TRICRITICAL BEHAVIOR MONTE-CARLO CRITICAL EXPONENTS phase-transitions O(4) MODEL SIMULATION ANISOTROPY

Electron Transport Property of CdTe under High Pressure and Moderate Temperature by In-Situ Resistivity Measurement in Diamond Anvil Cell

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Chinese Physics Letters 2007年第4期24卷 1070-1072页

作者：贺春元高春晓李明郝爱民黄晓伟张东梅于翠玲王月 State Key Laboratory for Superhard Materials Jilin University Changchun 130012 Department of Mathematics and Physics Hebei Normal University of Science and Technology Qinhuangdao 066004

In situ resistivity measurement has been performed to investigate the electron transport property of powered CdTe under high pressure and moderate temperature in a designed diamond anvil cell. Several abnormal resistivity changes can be found at room temperature when the pressure increases from ambient to 33 GPa. The abnormal resistivity changes at about 3.8 GPa and 10 GPa are caused by the structural phase transitions to the rock-salt phase and to the Cmcm phase, respectively. The other abnormal resistivity changes at about 6.5 GPa, 15.5 GPa, 22.2 GPa and about 30 GPa never observed before are due to the electronic phase transitions of CdTe. The origin of the abnormal change occurred at about 6.5 GPa is discussed. The temperature dependence of the resistivity of CdTe shows its semiconducting behaviour at least before 11.3 GPa.

关键词： phase-transitions III-V GPA

Dynamic Simulation of Kosterlitz-Thouless Transition in Two-Dimensional Fully Frustrated XY Model

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Chinese Physics Letters 2009年第1期26卷 216-219页

作者：雷晓蔚赵晓雨 Department of Physics Chongqing University of Arts and Sciences Chongqing 402160

Relaxation dynamics of the two-dimensional fully frustrated XY model is investigated with Monte Carlo methods. The simulation focuses on the Kosterlitz Thouless phase transition. From the dynamic scaling behaviour of the magnetization above the transition temperature TKT, the correlating time of the dynamic system is extracted. The transition temperature TKT and static exponent v are then determined.

关键词： NONEQUILIBRIUM CRITICAL-DYNAMICS MONTE-CARLO CRITICAL EXPONENTS phase-transitions SQUARE-LATTICE BEHAVIOR SYSTEMS SPIN X-Y model critical exponents Frustration phase transtormations Kosterlitz-Thouless transition Dynamic systems Spin Monte Carlo technique Transition Temperature Dynamic simulation

Undue Hardness/Modulus Ratio Claims instead of Physical Penetration Resistance and Applications with Mollusk Shells

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Advances in Materials Physics and Chemistry 2021年第2期11卷 45-57页

作者： Gerd Kaupp University of Oldenburg Oldenburg Germany

The Nanoindentation is a precise technique for the elucidation of mechanical properties. But such elucidation requires physically based interpretation of the loading curves that is widely still not practiced. The use of indentation hardness H and indentation modulus Er is unphysical and cannot detect the most important phase-transitions under load that very often occur. The claim that H versus E plots relate linearly for all different materials is neither empirically found nor correctly deduced. It is most dangerous by producing incorrect materials properties and misleading. The use of H/E (that is also called “elasticity index”) in complicated formulas for brittle parameter, yield strength, toughness, and so-called “true hardness” is also in error. The use of H/E cannot reveal the true qualities of materials without considering phase-transitions under load that require the correct exponent 3/2 on h for the loading curves (instead of disproved 2). This is exemplified with the physical data of different mollusk shells that experience phase-transitions, a new bionics model, and different contributions for their strengthening. The data are compared to the ones of aragonite and calcite and vaterite.

关键词： Nanoindentation H/E Ratio Challenge phase-transitions Penetration Resistance Mollusk Shells Aragonite Calcite Bionics