共查询到20条相似文献,搜索用时 0 毫秒
1.
Small angle neutron scattering (SANS) data for Undecylammonium chloride (UAC) in heavy water in the presence of NaCl 0.0428 and 0.3422 M are consistent with the presence of elongated micelles. This micellar shape has been adopted to analyze viscosity data of UAC in water in the presence of NaCl. The results obtained from this last technique are consistent with the increase of the micelle aggregation number with increasing the surfactant concentration. Micelles change from prolate ellipsoidal shape to cylindrical and wormlike shapes by increasing the added NaCl concentration and surfactant concentrations. The differences between results for the micelle aggregation number calculated from viscosity, SANS and light scattering data have been attributed to the solvent effect on micelle formation as well as changes in the size, shape and flexibility of the micelle. Viscosity data provide qualitative information on the effect of the added NaCl concentration and surfactant concentration on the size, shape, flexibility of the micelles in diluted solutions. 相似文献
2.
We calculate the configurational integral and reduced distribution functions for a system of four rigid spherical calottes, a model which allows an exact analysis of excluded-volume effects resulting from the interplay between statistics and geometry. 相似文献
3.
双轴向列相液晶的Monte Carlo模拟 总被引:1,自引:0,他引:1
利用Monte Carlo方法模拟棒状液晶分子随温度变化的相变行为,采用热力学统计方法得到能量与温度的关系,得出比热随温度的变化规律,通过图像的峰值确定相变点;重点模拟计算序参数矩阵元与温度的关系,得到不同分子结构参数下液晶系统的温度相图,模拟结果显示,当两个短棒长度相等时,不存在双轴相. 相似文献
4.
John F. Nagle 《Journal of statistical physics》1985,38(3-4):531-540
It has been suggested that some lattice models of polymers, especially ones that incorporate more realistic excluded volume interactions extending to further neighbors, may be subject to gridlock. A model is defined to have the property of gridlock if it cannot melt at any temperature unless a density decrease is allowed. Classical theories of polymer melting are incompatible with the property of gridlock. This paper proves rigorously that a two-dimensional square-lattice model of polymer chains that have nearest-neighbor excluded volume interactions (called the X1S model) has the gridlock property. The proof uses elementary concepts from graph theory. Also, different interpretations of the X1S model are given in terms of real polymers. This leads to a discussion of a number of different classes of melting depending upon whether the intramolecular rotameric energies and the attractive intermolecular energies are antagonistic to or supportive of the melting transition. 相似文献
5.
Sergei Kostromin Sergei Bronnikov Elena Perju Vasile Cozan 《Journal of Macromolecular Science: Physics》2013,52(11):2105-2112
Main-chain azomethine liquid crystal (LC) polymers varying in spacer length were studied using differential scanning calorimetry and polarizing optical microscopy. The nematic droplets appearing across the isotropic-nematic phase transition during cooling the polymer melt were treated statistically and their size distributions were described with equation based on the principles of irreversible thermodynamics. Kinetics of the ordered phase growth was described analytically with the universal law for cluster growth. Analysis of the mean LC droplet diameter as a function of time allowed recognition of two regimes of the ordered phase growth: i) nucleation and fast LC droplet growth and ii) consequent cluster coarsening. The length of the spacer in the polymer chain was shown to have an influence on the duration of the LC droplet growth regimes. 相似文献
6.
祝敬敏 《中国物理C(英文版)》2014,(10):9-14
We present a new model of quantum phase transitions in matrix product systems of one-dimensional spin-1 chains and study the phases coexistence phenomenon. We find that in the thermodynamic limit the proposed system has three different quantum phases and by adjusting the control parameters we are able to realize any phase, any two phases equal coexistence and the three phases equM coexistence. At every critical point the physical quantities including the entanglement are not discontinuous and the matrix product system has long-range correlation and N-spin maximal entanglement. We believe that our work is helpful for having a comprehensive understanding of quantum phase transitions in matrix product states of one-dimensional spin chains and of certain directive significance to the preparation and control of one-dimensional spin lattice models with stable coherence and N-spin maximal entanglement. 相似文献
7.
We present a new model of quantum phase transitions in matrix product systems of one-dimensional spin-1 chains and study the phases coexistence phenomenon. We find that in the thermodynamic limit the proposed system has three different quantum phases and by adjusting the control parameters we are able to realize any phase, any two phases equal coexistence and the three phases equal coexistence. At every critical point the physical quantities including the entanglement are not discontinuous and the matrix product system has long-range correlation and N-spin maximal entanglement. We believe that our work is helpful for having a comprehensive understanding of quantum phase transitions in matrix product states of one-dimensional spin chains and of certain directive significance to the preparation and control of one-dimensional spin lattice models with stable coherence and N-spin maximal entanglement. 相似文献
8.
《Molecular physics》2012,110(11-12):1269-1288
A generic equation of state (EoS) is developed for the hard cylindrical disc model to describe the isotropic phase of hard cut-sphere particles introducing a correction parameter to incorporate the negative contributions from higher-order virial coefficients. The isotropic–nematic–columnar phase diagram of hard cut-sphere fluids is investigated combining the new EoS with a scaled Onsager free energy for the nematic phase and an extended cell theory for columnar phase. By mapping the virial coefficients of an oblate spherocylinder on to those of the cylindrical disc (which are known algebraically), the new generic EoS is used to describe the isotropic and nematic phases of hard oblate spherocylinder particles. The predictions of the generic EoS are compared with available simulation data. 相似文献
9.
Learning physical states of bulk crystalline materials from atomic trajectories in molecular dynamics simulation 下载免费PDF全文
Tian-Shou Liang 《中国物理 B》2022,31(12):126402-126402
Melting of crystalline material is a common physical phenomenon, yet it remains elusive owing to the diversity in physical pictures. In this work, we proposed a deep learning architecture to learn the physical states (solid- or liquid-phase) from the atomic trajectories of the bulk crystalline materials with four typical lattice types. The method has ultra-high accuracy (higher than 95%) for the classification of solid-liquid atoms during the phase transition process and is almost insensitive to temperature. The atomic physical states are identified from atomic behaviors without considering any characteristic threshold parameter, which yet is necessary for the classical methods. The phase transition of bulk crystalline materials can be correctly predicted by learning from the atomic behaviors of different materials, which confirms the close correlation between atomic behaviors and atomic physical states. These evidences forecast that there should be a more general undiscovered physical quantity implicated in the atomic behaviors and elucidate the nature of bulk crystalline melting. 相似文献
10.
祝敬敏 《中国物理C(英文版)》2014,(12):11-15
For the matrix product system of a one-dimensional spin-1/2 chain, we present a new model of quantum2 phase transitions and find that in the thermodynamic limit, both sides of the critical point are respectively described by phases |Ψa 〉=|1··· 1 representing all particles spin up and |Ψb 〉=|0··· 0 representing all particles spin down, while the phase transition point is an isolated intermediate-coupling point where√ the two phases coexist equally, which is2 described by the so-called N-qubit maximally entangled GHZ state |Ψpt =√2/2(|1··· 1 +|0··· 0). At the critical point,2the physical quantities including the entanglement are not discontinuous and the matrix product system has longrange correlation and N-qubit maximal entanglement. We believe that our work is helpful for having a comprehensive understanding of quantum phase transitions in matrix product states of one-dimensional spin chains and of potential directive significance to the preparation and control of one-dimensional spin lattice models with stable coherence and N-qubit maximal entanglement. 相似文献
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12.
Density functional theory of freezing of a system of highly elongated ellipsoidal oligomer solutions
Shikha Dwivedi 《Phase Transitions》2017,90(5):509-523
We have used the density functional theory of freezing to study the liquid crystalline phase behavior of a system of highly elongated ellipsoidal conjugated oligomers dispersed in three different solvents namely chloroform, toluene and their equimolar mixture. The molecules are assumed to interact via solvent-implicit coarse-grained Gay–Berne potential. Pair correlation functions needed as input in the density functional theory have been calculated using the Percus–Yevick (PY) integral equation theory. Considering the isotropic and nematic phases, we have calculated the isotropic–nematic phase transition parameters and presented the temperature–density and pressure–temperature phase diagrams. Different solvent conditions are found not only to affect the transition parameters but also determine the capability of oligomers to form nematic phase in various thermodynamic conditions. In principle, our results are verifiable through computer simulations. 相似文献
13.
For the matrix product system of a one-dimensional spin-1/2 chain, we present a new model of quantum phase transitions and find that in the thermodynamic limit, both sides of the critical point are respectively described by phases |Ψa>=|1…1> representing all particles spin up and |Ψb>=|0…0> representing all particles spin down, while the phase transition point is an isolated intermediate-coupling point where the two phases coexist equally, which is described by the so-called N-qubit maximally entangled GHZ state |Ψpt>=√2/2(|1…1>+|0…0>). At the critical point, the physical quantities including the entanglement are not discontinuous and the matrix product system has long-range correlation and N-qubit maximal entanglement. We believe that our work is helpful for having a comprehensive understanding of quantum phase transitions in matrix product states of one-dimensional spin chains and of potential directive significance to the preparation and control of one-dimensional spin lattice models with stable coherence and N-qubit maximal entanglement. 相似文献
14.
用变温拉曼光谱对相变过程的研究表明,液晶化合物的初始晶态与熔融后缓慢降温得到的晶态并不吻合,两个状态下分子尾链的构象及刚性核部分的构象不同导致分子的聚集状态不同。西佛碱型液晶化合物VO10相变过程中,在晶态到液晶态相转变过程中,烷氧基尾链链内构象发生突变,同时有序性降低,刚性核部分两个苯环之间的二面角在相变点时发生明显变化,二面角加大。 相似文献
15.
用强度补偿式光纤位移传感器测量液体体胀系数具有稳定性好、精度高、安全可靠等优点,可以减小用光杠杆法、干涉法、CCD法等测量方法在操作方面带来的麻烦,也能进一步拓宽这种光纤传感器的应用范围。 相似文献
16.
Grover根据实验数据给出,液态金属的定容比热随温度近似线性减小:cV≈3R-ζRT/Tm,式中T为温度,Tm为熔化温度,R为普适气体常数,ζ为经验常数,其值在0.11至0.24之间,就平均来说,ζ≈0.15。利用Lennard-Jones-Devonshire理论对这一经验关系进行了解释。 相似文献
17.
微流动驱动的胶体自组装是一种非平衡的过程。在定向微流动(如热毛细流)驱动下,胶体体系内的粒子自身的热运动受到抑制,胶体体系中的微粒常常出现宏观有序的结构。但这种粒径的球在重力作用下会显著沉降,造成胶体体系的浓度不均,而胶体体系的相行为与浓度密切相关。因此在重力作用下难以准确地描述相变与局域结构的关联。在微重力条件下,大尺度的胶体球没有重力沉降作用,可提供准确的局域结构信息,而且浮力对流受到较大抑制,没有流体静压力,不产生沉降作用,这为研究界面上的胶体自组装动力学行为提供了有利条件。“胶体有序排列及新型材料研究”是“实践十号卫星”19项科学实验载荷之一,其科学实验将在载荷“胶体材料箱”中完成,将是空间中进行的首次胶体自组装动力学行为的实验研究。 相似文献
18.
A phenomenological model of the transition from quark-gluon phase to hadron phase is presented on the analogy of BCS theory. The massive current-quarks constitute the quark Cooper-pair, i.e., the hadron at Tc = 150~200 MeV, The order parameter of qq-pair takes a value in the range from 0.4 to 0.2 GeV. An experimental verification method of the present model in the heavy-ion collision is proposed. 相似文献
19.