Theoretical Studies of Phase transition of a Magnetic Binary Mixture

根据二元混合热力学原理我们计算了带磁性的二元混合体系的自由能，并利用平均场理论中的Bragg-Williams理论讨论分析了等组分体系φ=0.5和不等组分体系φ<0.5的相变和相图。结果表明：1、不考虑摇摆（staggered）效应ms=0，二元磁性混合体系存在二阶相变。相变温度T/znJ1、不同类粒子间与同类粒子间相互作用强度比J2/J1和体积比φ的关系为T/znJ1=2φ2(1-J2/J1)-2φ(1-J2/J1)+1；（1）不同类粒子间与同类粒子间相互作用强度比J2/J1>1时，即J2不同类粒子间相互作用占主导地位，体积比φ在两端处，即其中一种组分较少，二阶相变的温度T/zn...Using the thermodynamics of binary mixtures, we calculate the free energy of a magnetic binary mixture. The phase transitions inφ=0.5 binary mixtures andφ<0.5 binary mixtures are analyzed and discussed using mean-field Bragg-Williams theory. It is found that.1. Without staggering effect, there exists a second-order phase transition in a binary mixed magnetic system. The relation between phase...学位：理学硕士院系专业：物理与机电工程学院物理学系_理论物理学号：X20032400

Self-interaction Correction to Density-functional Approximations

用一种简单的方法说明任何能量的密度泛函的自相互作用修正(SIC)。自相互作用的单电子势采用变分原理。在Hohenberg—Kohn理论框架下,通过引进了与轨道无关的单粒子势,和在Kohn-Sham框架下的局域势来修正。应用于一些用LSD方法会产生系统误差的物理问题上。结果表明当充分改进它的形状描述时,它正确收敛与交换关联域数值一致。We present one simply method for the self-interaction (SIC) of any density functional for the energy; correction of the self-consistent one-electron potential follows naturally from the variational principle. Our methods is sanctioned by the Hohenberg-Kohn theorem. We apply the method to LSD and show that it properly conserves the number content of the exchange-correlation hole, while substantially improving the description of its shape

二元磁性等组分混合体系的相变

基于二元混合热力学原理,计算了二元磁性混合体系的自由能,并应用平均场理论中的Bragg-Williams理论,分析讨论了等组分体系的相变和相图。结果表明:1)不考虑摇摆(Staggered)效应,二元磁性混合体系存在二阶相变。2)考虑摇摆效应时,等组分二元磁性混合体系在不同类粒子间相互作用强度与同类粒子间相互作用强度J2/J1较小时,存在二阶相变。国家自然科学基金项目,批准号:10225420、90206039、20021002;; 福建省自然科学基金项目,批准号:A021001

Monte Carlo simulation of chromatin fiber conformation affected by ionic strength

通过核小体纤维模型的构建,利用MontoCarlo方法模拟其在各种钠离子浓度的溶液中结构变化的过程.模拟结果显示当溶液的钠离子浓度增大时,核小体由锯齿状结构转变为螺旋状结构.在常温所得到的核小体结构参数与实验结果接近,较好地解释了溶液中的钠离子浓度对核小体纤维结构的影响.In this paper, using Monte Carlo simulation, we obtain different structures of chromatin fibers with different ionic concentration. The result shows that as the ionic concentration is increased, the fiber undergoes a conformational change from sawtooth state to super-helix state. The structural parameters obtained by simulation agree well with the experimental results, indicating that our model is useful in explaining the conformational change of chromatin fibers in different ionic solutions.国家自然科学基金(批准号:10225420,90206039,20021002)资助的课题~