FCC ISING-MODEL IN CLUSTER VARIATION APPROXIMATION
FCC ISING-MODEL IN CLUSTER VARIATION APPROXIMATION
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DOI：
10.1103/physrevb.17.2926
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发表时间：
1978-01-01
影响因子：
3.7
通讯作者：
FONTAINE, DD
中科院分区：
文献类型：
--
作者：
SANCHEZ, JM;FONTAINE, DD
用集团变分法计算了面心立方伊辛铁磁体在三种不同集团近似下的临界温度。本文提出了一种确定一组独立的团簇变量的方法，大大简化了自由能的极小化。从这样的最小化所产生的方程组求解，在无序状态下，通过一个简单的迭代技术。在这项工作中处理的最高水平的近似产生的临界温度，这是只有1.5%以上的零场磁化率的精确高温膨胀估计。此外，比热的高温膨胀给出了四个精确的系数，第五个系数被确定为在0.4%以内。
The cluster-variation method was used to calculate the critical temperature for the fcc Ising ferromagnet in three different cluster approximations. A scheme for determing a set of independent cluster variables is presented, which considerably simplifies the minimization of the free energy. The system of equations arising from such minimization is solved, in the disordered state, by means of a simple iteration technique. The highest level of approximation treated in this work yields a critical temperature which is only 1.5% above the one estimated by the exact high-temperature expansion of the zero-field susceptibility. Furthermore, the high-temperature expansion for the specific heat gives four exact coefficients and the fifth is determined to within 0.4%.