液体的内压和内能的统计热力学理论

利用分布函数理论导出了液体的内能和内压公式.液体的内压和过剩内能可以表示成体积的幂级数形式,其中的系数可以用多体相互作用势和多体径向分布函数表出,它们仅仅与温度有关.讨论了液体仅存在第n次多体相互作用势情形的内压和过剩内能的表达式,结果与Egelstaff的微扰理论结果具有相同的形式,不仅给出了相应参数的表达式而且适用于多体相互作用较强的情形.定义了物性参数α(T)和m,得到的液体过剩内能和内压的表达式与Frank实验结果具有相同的形式,其结果不仅给出了参数α(T)和m的表达式,而且指出了Frank的过剩内能和内压公式只适用于参数α(T)和m与体积无关的液体.

Inner Pressure and Inner Energy of the Liquid

The formulas of inner pressure and inner energy of the liquid are derived using distribution function theory. During the derivation three characters of interaction potential energy of the liquid are assumed. The first is that the interaction force between molecules is the short-range force. The second is that the many-body potential is only relying on the distances between the molecules. The third is that the potential energy of the liquid can be written as the sum of a series of many-body potential . The inner pressure and inner energy can be expressed in the power series of the volume. The coefficients in the series are expressed in many-body potential and radial distribution functions and are only depend on temperature. When onlynth many-body potential is exist, the formula of inner pressure and inner energy are in agreement with the result of perturbation theory obtained by Egelstaff. The results not only give the expressions for parameters but also are suitable for stronger interaction between molecules. Another form of expressions of inner pressure and inner energy is obtained by defining parametersmandα(T). The expressions agreed with the experimental result worked out by Frank. The results give the expressions for parametersmandα(T)and point out that the Frank formulas are tenable only for the liquid which mandα(T)are independent of volume.