摘要:
利用路径积分蒙特卡罗(PIMC)模拟方法研究了由256个~4He原子组成的系统在不同条件下的对关联函数g(r).在标准大气压下(SVP),分别在1.38 K,1.67 K,2.50 K和4.24 K等四个温度时对系统不同势能的情况的对关联函数进行了计算;另外还讨论了系统的温度和密度对对关联函数的影响.结果发现,系统的势能变化及密度变化都或大或小影响对关联函数,而温度对其影响不是很大.虽然PIMC方法存在有限尺度效应,但是由128和256个~4He原子组成系统的对关联函数存在极小的差异,因此可以得到:随着模拟系统尺度的增大,所模拟的有限尺度的系统已逐渐接近于真实系统.所以所得的256原子系统的性质可近似说明液态系统性质.
Abstract:
Path integral Monte Carlo (PIMC) simulation is a powerful tool in studying the interacting quantum systems at finite temperatures. In this article, we use PIMC to study the pair correlation function g(r) of the system consisting of 124 ~4He atoms in different conditions. At saturated-vapor-pressure (SVP), we calculated the pair correlation function g (r) at four different temperatures respectively, that is, T= 1.38 K, 1.67 K, 2.50 K and 4.24 K. We also determined the changes in g(r) when either temperature or density is changed while the other remaines fixed, and found that for different densities and the same temperature, the change in g (r) is remarkable, while for different temperatures but same density, the change is not obvious. We used the microcosmic point of view for g(r) to explain the above phenomenon. Although finite size effects exist in the PIMC method, when comparing the pair correlation function belonging to systems consisted of 128 and 256 ~4He atoms respectivdy, differences between them are small. And we can conclude that as the increasing of the simulated system size, differences between simulated system and the real one becomes smaller and smaller. So in this particle, the properties educed from the simulated system consisted of 256 4 He atoms can represent those of the real liquid system.
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