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Ab-initio molecular dynamics simulation on nano-system under external pressure

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science china Mathematics 2004年第z1期47卷 92-100页

作者： Jl Min, SUN Deyan & GONG XingaoSurface physics Laboratory and Department of physics, Fudan University, Shanghai 20043., china Institute of Solid State physics, chinese academy of sciences, Hefei 23.03., china Interdisciplary center for theoretical studies, chinese academy of sciences, Beijing 100080, china Fudan Univ Surface Phys Lab Shanghai 200433 Peoples R China Fudan Univ Dept Phys Shanghai 200433 Peoples R China chinese Acad Sci Inst Solid State Phys Hefei 230031 Peoples R China chinese Acad Sci Interdisciplinary Ctr Theoret Studies Beijing 100080 Peoples R China

A new constant-pressure molecular dynamics (MD) method is developed to simulate the dynamic behavior and structure transition of finite system under external pressure. In this method, no artificial parameter is introduced and the computation overheads are very small. As an application, a hard-soft transition of single wall carbon nanotube (SWCNT) under external pressure is found, which is in agreement with the experiments.

关键词： phase transition, simulation, nano-particles

The gravity wave instability induced by photochemistry in summer polar mesopause region

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chinese science Bulletin 2000年第3期45卷 267-272页

作者： center for Space science and Applied Research, chinese academy of sciences, Beijing 100080, {3. Laboratory of Numeric Study of Heliospheric physics, chinese academy of sciences, Beijing 100080, {3. center for Space science and Applied Research Chinese Academy of Sciences Beijing China Laboratory of Numeric Study of Heliospheric physics Chinese Academy of Sciences Beijing China

The effect of diabatic process due to the photochemical heating and cooling on the gravity wave propagation in middle atmosphere is studied. A linear gravity wave model which considers the diabatic process is established. The unstable region and the growth rate of the gravity wave caused by photochemistry are calculated. And the comparison between the model and the adiabatic gravity wave theory of pure dynamics is made. The results indicate that the photochemical heating process can induce the instability of gravity wave at mesopause. The intensity of the instability becomes stronger as the temperature decreases. The temperature feature and the altitude characteristics of the instability are consistent with the observation. Therefore, the instability of the gravity wave induced by photochemistry may be an important mechanism in polar mesopause region in summer.

关键词： photochemistry instability gravity wave growth rate.

Statistical theory for hydrogen bonding fluid system of A_aD_d type (I): The geometrical phase transition

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science china Chemistry 2006年第6期49卷 499-506页

作者： WANG Haijun1,2, HONG Xiaozhong3. GU Fang1 & BA Xinwu1 1. College of Chemistry and Environment science, Hebei University, Baoding 071002, china 2. International center for Materials {3., chinese academy of sciences, Shenyang 110016, china 3. College of {3. science and Technology, Hebei University, Baoding 071002, china 1. College of Chemistry and Environment science Hebei University Baoding 071002 China 2. International center for Materials physics Chinese Academy of Sciences Shenyang 110016 China 3. College of physics science and Technology Hebei University Baoding 071002 China

The influence of hydrogen bonds on the physical and chemical properties of hydrogen bonding fluid system of AaDd type is investigated from two viewpoints by the principle of statistical mechanics. In detail, we proposed two new ways that can be used to obtain the equilibrium size distribution of the hydrogen bonding clusters, and derived the analytical expression of a relationship between the hydrogen bonding free energy and hydrogen bonding degree. For the nonlinear hydrogen bonding systems, it is shown that the sol-gel phase transition can take place under proper conditions, which is further proven to be a kind of geometrical phase transition rather than a thermodynamic one. Moreover, several problems associated with the geometrical phase transition and liquid-solid phase transition in nonlinear hydrogen bonding systems are discussed.

关键词： hydrogen bonding fluid, equilibrium free energy, geometrical phase transition.

Lepton flavor violating Z-boson decays at GigaZ as a probe of supersymmetry

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science china(physics,Mechanics & Astronomy) 2010年第11期53卷 1949-1952页

作者： YANG JinMin 1,2 1 Department of physics,Henan Normal University,Xinxiang 453.07,china 2 Institute of theoretical physics,chinese academy of sciences,Beijing 100190,china 1. Department of physics Henan Normal University Xinxiang 453007 China2. Institute of Theoretical Physics Chinese Academy of Sciences Beijing 100190 China

This paper briefly reviews the lepton flavor violating Z-decays at GigaZ as a probe of supersymmetry by focusing on Z → i j in two representative supersymmetric models: the minimal supersymmetric model without R-parity and the supersymmetric seesaw *** work concludes that under the current experimental constraints from LEP and i → j γ,these rare decays can still be enhanced to reach the sensitivity of the ***,supersymmetry can be probed via these decays at GigaZ.

关键词： Z-decay GigaZ supersymmetry

New evidence for lack of CMB power on large scales

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science china(physics,Mechanics & Astronomy) 2010年第3期53卷 567-570页

作者： LIU Hao1 & LI TiPei1,2,3.1 Key Laboratory of Particle Astrophysics, Institute of High Energy physics, chinese academy of sciences, Beijing {3., china 2 Department of physics & center for Astrophysics, Tsinghua University, Beijing 100084, china 3.Department of Engineering physics & center for Astrophysics, Tsinghua University, Beijing 100084, china 1. Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China2. Department of Physics & Center for Astrophysics Tsinghua University Beijing 100084 China3. Department of Engineering Physics & Center for Astrophysics Tsinghua University Beijing 100084 China

A digitalized temperature map is recovered from the first light sky survey image published by the Planck team, from which an angular power spectrum of the cosmic microwave background (CMB) is derived. The amplitudes of the low multipoles (low-l) measured from the preliminary Planck power spectrum are significantly lower than those reported by the WMAP team. Possible systematical effects are far from enough to explain the observed low-l differences.

关键词： cosmology cosmic microwave background data analysis

Patterns of platinum-group elements in mantle peridotite, granulite xenoliths and basalt in Hannuoba

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chinese science Bulletin 1999年第18期44卷 1676-1681页

作者： CHU Xuelei, LI Xiaolin, XU Jiuhua and LIU Jianming1. The Research center of Mineral Resources Exploration , chinese academy of sciences , Beijing 100101, china 2. Institute of Geology , chinese academy of sciences , Beijing 100029, china 3. Institute of High Energy physics , chinese academy of sciences , Beijing 100817 , china 4. Beijing University of science and Engineering , Beijing 100083. china Corresponding author The Research center of Mineral Resources Exploration Chinese Academy of Sciences Beijing China Institute of Geology Chinese Academy of Sciences Beijing China Institute of High Energy physics Chinese Academy of Sciences Beijing China Beijing University of science and Engineering Beijing China

Neutron activation analysis after preconcentration of nickel sulfide fire assay was used in measurement of Ru, Ph, Pd, Os, Ir, Pt (i.e. PGE elements) and Au concentrations for basalt, mantle and granulite xenoliths in Hannuoba. The chondrite- and primitive mantle-normalized PGE patterns generally exhibit flat (for Iherzolite), negative slope (for harzburgite),

关键词： mantle xenolith granulite xenolith basalt platinum-group element Hannuoba.

Charmed Baryon in Diquark Model

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原子核物理评论 2009年第S1期26卷 190-193页

作者： WANG Qing-wu1,3. ZHANG Peng-ming1,2(1 Institute of Modern physics, chinese academy of sciences, Lanzhou 73.000, china 2 {3. of theoretical Nuclear physics, National Laboratory of Heavy Ion Research Facility in Lanzhou,Lanzhou 73.000, china 3.Graduate School of chinese academy of sciences, Beijing 100049, china) Institute of Modern physics Chinese Academy of SciencesLanzhou 730000China Graduate School of chinese academy of sciences Beijing 100049China Institute of Modern physics Chinese Academy of SciencesLanzhou 730000China center of theoretical Nuclear physics National Laboratory of Heavy Ion Research Facility in LanzhouLanzhou 730000China

A diquark model is used to investigate single-charmed baryons. In this model,baryon is composed of two diquarks and an antiquark. Masses of lowest lying states with JP=1/2± are obtained. Baryons in our results are as heavy as other theoretic predictions and we suggest that the five-quark components should be considered in any three-quark model for studying the charmed baryons.

关键词： charm diquark pentaquark

From quantum spectra to classical orbits: Varying rectangular billiards

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Progress in Natural science:Materials International 2008年第8期18卷 927-930页

作者： Jun Lu * Department of Foundational science, Beijing Union University, Beijing 100101, china Institute of theoretical {3., chinese academy of sciences, Beijing 100080, china Department of Foundational science Beijing Union University Beijing 100101 China Institute of theoretical physics Chinese Academy of Sciences Beijing 100080 China

The quantum-spectrum function is introduced by means of the eigenvalues and the eigenfunctions in the system of varying rectangular billiards. It is found that the Fourier transform of the quantum-spectrum function corresponds with the classical orbits in the system. These results give new evidence about the classical-quantum correspondence.

关键词： Quantum spectrum Classical-quantum correspondence Semiclassical physics

A one-dimensional heat transfer model of the Antarctic Ice Sheet and modeling of snow temperatures at Dome A, the summit of Antarctic Plateau

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science china Earth sciences 2010年第5期53卷 763-772页

作者： CHEN BaiLian1,3. ZHANG RenHe2, SUN ShuFen1, BIAN LinGen2, XIAO CunDe4,2 & ZHANG TingJun5 1 Institute of Atmospheric physics, chinese academy of sciences, Beijing 100029, china 2 {3. academy of Meteorological sciences, Beijing 100081, china 3.Graduate University of chinese academy of sciences, Beijing 100049, china 4 Cold and Arid Regions Environmental and Engineering Research Institute, chinese academy of sciences, Lanzhou 73.000, china 5 The National Snow and Ice Data center, University of Colorado, Boulder, CO 803.9-0449, USA 1. Institute of Atmospheric physics Chinese Academy of Sciences Beijing 100029 China3. Graduate University of Chinese Academy of Sciences Beijing 100049 China2. Chinese Academy of Meteorological Sciences Beijing 100081 China4. Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China5. The National Snow and Ice Data Center University of Colorado Boulder CO 80309-0449 USA

A vertical one-dimensional numerical model for heat transferring within the near-surface snow layer of the Antarctic Ice Sheet was developed based on simplified parameterizations of associated physical processes for the atmosphere, radiation, and snow/ice systems. Using the meteorological data of an automatic weather station (AWS) at Dome A (80°22′S, 70°22′E), we applied the model to simulate the seasonal temperature variation within a depth of 20 m. Comparison of modeled results with observed snow temperatures at 4 measurement depths (0.1, 1, 3. 10 m) shows good agreement and consistent seasonal variations. The model results reveal the vertical temperature structure within the near-surface snow layer and its seasonal variance with more details than those by limited measurements. Analyses on the model outputs of the surface energy fluxes show that: 1) the surface energy balance at Dome A is characterized by the compensation between negative net radiation and the positive sensible fluxes, and 2) the sensible heat is on average transported from the atmosphere to the snow, and has an evident increase in spring. The results are considered well representative for the highest interior Antarctic Plateau.

关键词： Antarctic Ice Sheet near-surface layer energy transfer numerical model