共查询到20条相似文献,搜索用时 31 毫秒
1.
Robert Schrader 《Journal of statistical physics》1985,40(3-4):533-561
In a Monte Carlo computer experiment, we simulate the Gibbs distribution of nonconnected two-dimensional surfaces isometrically embedded in three-dimensional Euclidean space with fixed boundary and the action given by the area. The simulation involves surfaces built out of plaquettes in a cubical lattice. The foam structure is analyzed in terms of correlations of the local fluctuations in the Euler characteristic and the area. The scaling behavior of the area and the Euler characteristic is discussed by varying the boundary. We show evidence of a phase transition point which is independent of the choice of the boundary. An existence proof is given of the thermodynamic limit for the models considered.Supported in part by the Deutsche Forschungsgemeinschaft and NSF grant No. Phy 81 09110A 01. 相似文献
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U. Glaus 《Journal of statistical physics》1988,50(5-6):1141-1166
Two models of self-avoiding surfaces on the cubic lattice are studied by Monte Carlo simulations. Both the first model with fluctuating boundary and the second one with a fixed boundary are found to belong to the universality class of branched polymers. The algorithms as well as the methods used to extract the critical exponents are described in detail. The results are compared to other recent estimates in the literature. 相似文献
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Purvee Bhardwaj Sadhna Singh Neeraj Kumar Gaur 《Central European Journal of Physics》2008,6(2):223-229
In the present paper we have investigated the high-pressure, structural phase transition of Barium chalcogenides (BaO, BaSe
and BaTe) using a three-body interaction potential (MTBIP) approach, modified by incorporating covalency effects. Phase transition
pressures are associated with a sudden collapse in volume. The phase transition pressures and associated volume collapses
obtained from TBIP show a reasonably good agreement with experimental data. Here, the transition pressure, NaCl-CsCl structure
increases with decreasing cation-to-anion radii ratio. In addition, the elastic constants and their combinations with pressure
are also reported. It is found that TBP incorporating a covalency effect may predict the phase transition pressure, the elastic
constants and the pressure derivatives of other chalcogenides as well.
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With the full treatment of the Helfrich model we theoretically study the symmetrical adhesion of two cylindrical colloids to a tubular membrane. The adhesion of the rigid cylinders with different radius from the membrane tube surface can produce both shallow wrapping with relatively small wrapping angle and deep wrapping with big wrapping angle. These significant structural behaviors can be obtained by analyzing the system energy. A second order adhesion transition from the desorbed to weakly adhered states is found, and a first order phase transition where the cylindrical colloids undergo an abrupt transition from weakly adhered to strongly adhered states can be obtained as well. 相似文献
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The generalized Curie-Weiss model is an extension of the classical Curie-Weiss model in which the quadratic interaction function of the mean spin value is replaced by a more general interaction function. It is shown that the generalized Curie-Weiss model can have a sequence of phase transitions at different critical temperatures. Both first-order and second-order phase transitions can occur, and explicit criteria for the two types are given. Three examples of generalized Curie-Weiss models are worked out in detail, including one example with infinitely many phase transitions. A number of results are derived using large-deviation techniques. 相似文献
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The nature of inverse velocity surfaces as well as energy surfaces for elastic wave propagation in the (111) plane have been
studied for a number of cubic crystals. The sections of inverse velocity surfaces by the (111) plane exhibit six-fold symmetry
in all cases. Cuspidal edges are exhibited with a six-fold symmetry by both the slow transverse and fast transverse shear
modes in the (111) plane, unlike the case of the (100) and (110) planes for which only the slow transverse shear mode exhibits
cuspidal edges. The slow transverse mode energy surface exhibits cuspidal edges along
direction or an equivalent symmetry direction. The inverse velocity surfaces of the A-15 compounds exhibit unusually large
inflexions for the slow transverse mode, whereas their energy surfaces have large cuspidal edges which intersect each other
resulting in common regions of cusps. 相似文献
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对化学自由能模型进行系统性的研究,着重分析化学反应动态平衡条件下粒子组分的求解方案,提出应用模拟退火算法寻找自由能密度函数极小值点的求解方案.该方案同时解决了两个难题:1)在一级相变区化学势平衡方程组可能遇到多个解而无法甄别其物理意义.通过模拟退火算法定位到自由能密度函数曲面的最低点,因而可从多个解中甄别出稳定的热力学平衡态.2)模拟退火算法用随机的"热涨落"消除初值敏感性,因而可采用同一套初值计算不同的温度密度点,为实现宽区域上大量温度密度点的连续快速计算奠定基础.作为该平衡态求解方案的应用,计算氦流体在"等离子相变"区的物态方程,揭示了丰富的"等离子相变"现象,并与第一性原理计算揭示的氢流体"液液相变"现象进行类比. 相似文献
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Deoshree Baghmar Neeraj K. Gaur Dinesh C. Gupta Sadhana Singh 《Central European Journal of Physics》2008,6(3):445-449
The structural changes within the Silver iodide (AgI) and Copper iodide (CuI) induced by pressure have been investigated using
an effective interaction potential. CuI and AgI in their parent zinc blende (ZnS) to rock salt (NaCl) through an intermediate
structure have been reported. The calculated values for the phase transition pressures and associate volume collapses are
generally in good agreement with measured data.
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Deoshree Baghmar 《Phase Transitions》2013,86(8):811-823
The structural phase transformations in various phases (monoclinic, ortho I, ortho II, and tetragonal) of zirconia (ZrO2) have been investigated using an effective interionic interaction potential. The cohesive energy, the equation of state, and the elastic properties of these phases have also been studied and found to reproduce well the experimentally observed data for almost all the phases of zirconia ceramics. 相似文献
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We used the molecular dynamics simulation with interatomic potentials of the embedded atom method to calculate the high-index surface energies of the surfaces containing the 〈0 0 1〉 axis or 〈−1 1 0〉 axis in f.c.c. metal Al, Cu and Ni at zero temperature. We generalized an empirical formula based on structural unit model for high-index surfaces and present some new formulas that can be used to estimate the surface energy and structural feature of high-index surfaces very well. The results show that the closest surfaces have the lowest surface energy and the surface energies of the closest (1 1 1) surface and the next closest (1 1 0), (1 0 0) surfaces are the extremum on the curve of surface energy versus orientation angle. We also calculated the b.c.c. metal Fe and obtained a similar result. The difference is that in the b.c.c. metal the surface energies of the closest (1 1 0) surface and the next closest (1 0 0), (1 1 2) surfaces are the extremum on the curve of surface energy versus orientation angle. The results of theoretical simulation and the empirical formula consist well with the experiment data. 相似文献
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原子核的形状演化效应是核结构研究的重要基础问题之一。通常认为,A=160质量区的奇A核位于大形变核区域,它们的激发态能谱将呈现出典型的转动激发特征。然而,基于E-GOS曲线方法,发现随着角动量的增加,该质量区奇A核的晕带具有显著地从转动激发演化成为振动激发的形状演化现象。此外,为深入理解原子核形状演化的微观机制,采用Total-Routhian-Surface(TRS)方法针对稀土区的奇A核进行了理论计算,结果表明,165Yb和157Dy同位素在低激发态时具有稳定的长椭形变,当角动量大于0.50 MeV后,核芯的四极形变显著减小并开始产生三轴形变。The phase transition of nuclei with increasing angular momentum (or spin) and excitation energy is one of the most fundamental topics of nuclear structure research. The odd-N nuclei with A ≈160 are widely considered belonging to the well-deformed region, and their excitation spectra are energetically favored to exhibit the rotational characteristics. In this work, however, the evidence suggesting that the nuclei changes from rotation to vibration along the yrast lines as a function of spin was found. The simple method, named as E-Gamma Over Spin (E-GOS) curves, would be used to discern the evolution from rotational to vibrational structure in nuclei for various spin ranges. Meanwhile, in order to understand the band structure properties of nuclei, theoretical calculations have been performed for the yrast bands of the odd-A rare-earth nuclei within the framework of the total routhian surface (TRS) model. The TRS plots predict that the 165Yb and 157Dy isotopes have large quadrupole shapes at low spin states. At higher rotational frequency (hω~ >0.50 MeV), a clear reduction of the quadrupole deformation is indicated by the present results, and the isotopes become rigid in the γ deformation. 相似文献
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简单介绍了文章作者在半导体硅重构表面及其相变动力学研究方面的进展.近期Si(111) (7×7)-(1×1)相变的实验研究发现,将温度升高到相变温度以上时,7×7岛面积以恒定的衰减速率随时间减小至零,且初始面积越大的岛这个衰减速率就越大.文章作者分析了大量的实验事实,由此提出了一个双速相场模型来解释这个重要而令人困惑的现象.模型重点是:在相变过程中,7×7关键结构变化较快,随后的层错消解过程要慢得多.这个模型完美地解释了相关实验现象,说明该模型抓住了关键物理要素,这种相场方法也可以用于其他半导体表面相变研究. 相似文献
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The general expressions for the compliance , Young's modulus E(h k l) and Poisson's ratio υ(h k l) along an arbitrary direction [h k l] are given for cubic crystals. The representation surfaces, for which the length of the radius vector in the [h k l] direction equals to E(h k l) or υ(h k l), are constructed for seven BCC transition metals Cr, Fe, Mo, Nb, Ta, V and W. Neglecting W, which is isotropic, both representation surfaces of Young's modulus and Poisson's ratio are spherical surfaces. The remaining BCC transition metals may be grouped into two classes. In the first group (Cr, Mo, Nb and V) with negative values of sA, Young's modulus surface has eight depressed corners and six rounded protuberances at the centers of the faces. In the second group (Fe and Ta) with positive values of sA, on the contrary, Young's modulus surface has eight rounded protuberance corners and six depressions at the centers of the faces. The contrary conclusions are obtained for Poisson's ratio. 相似文献
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Structural stability of TiO and TiN under high pressure 总被引:1,自引:0,他引:1
The high pressure phase transition and elastic behavior of Transition Metal Compounds (TiO and TiN) which crystallize in NaCl-structure
have been investigated using the three body potential model (TBPM) approach. These interactions arise due to the electron-shell
deformation of the overlapping ions in crystals. The TBP model consists of a long range Coulomb, three body interactions,
and the short-range overlap repulsive forces operative up to the second neighboring ions. The authors of this paper estimated
the values of the phase transition pressures, associated volume collapses, and elastic constants, all of which were found
to be closer to available experimental data than other calculations. Thus, the TBPM approach promises to predict the phase
transition pressure and pressure variations of elastic constants of Transition Metal compounds.
相似文献