长程相互作用Blume-Emery-Griffiths模型:微正则系综的临界指数

我们研究了长程Blume-Emery-Griffiths模型在微正则系综下的热力学量,发现在一级相变附近不仅出现负比热,磁化率也呈现负值,并且温度、比热和磁化率在一级相变点都不连续.当系统发生有序-无序的二级相变时,比热的临界指数a=a′=0和磁化率的临界指数γ=γ′=1与平均场的结果一致.当耦合常数对应于正则系综的三临界点时,比热的临界指数0=a≠a′=1和磁化率的临界指数1=γ≠γ′=2被获得.我们发现临界指数关系a′+β+γ′>2破坏Widom标度律和等价性.

Long-range interaction Blume-Emery-Griffiths model:Critical exponents in microcanonical ensemble

We investigate the thermodynamic quantities of Blume-Emery-Griffiths model with long-range interactions and observe negative specific heat and susceptibility near the first order line,where the temperature,specific heat and susceptibility are discontinuity.When order-disorder phase transition takes place,the critical exponent of specific heat（a=a＇=0） and the critical exponent of susceptibility（γ=γ＇=1） are consistent with the prediction of mean field theory.However,when coupling constant corresponds to the value of canonical tri-critical point,the critical exponent of specific heat and susceptibility take the values of 0=a≠a＇=1 and 1=γ≠γ＇=2.The critical exponents violate the scaling homogeneity equalities and a＇＋β＋γ＇2 breaks down the Widom scaling law.