Misumi Yuji, Masatsuji Satoru, Sahara Ryoji, Ishii Soh, Ohno Kaoru
Department of Physics, Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya, Yokohama 240-8501, Japan.
J Chem Phys. 2008 Jun 21;128(23):234702. doi: 10.1063/1.2938181.
Although a lattice Monte Carlo method provides an effective, simple, and fast way to study thermodynamic properties of substitutional alloys, it cannot treat by itself the off-lattice effects, such as thermal vibrations and local distortions. Therefore, even if the interaction among atoms at lattice points is calculated accurately by means of first-principles calculations, the lattice Monte Carlo simulation overestimates the order-disorder phase transition temperature. In this paper, we treat this problem in the investigation of the FePt alloy, which has recently attracted considerable interest in its magnetic properties. We apply a simple version of the potential renormalization theory to determine the interaction among atoms, including partly the off-lattice effects by means of first-principles calculations. Then, we use the interaction to perform a lattice Monte Carlo simulation of the FePt alloy on a fcc lattice. From the results, we find that the transition temperature obtained after the present renormalization procedure becomes closer to the experimental value.
尽管晶格蒙特卡罗方法为研究替代合金的热力学性质提供了一种有效、简单且快速的途径，但它自身无法处理非晶格效应，诸如热振动和局部畸变。因此，即便通过第一性原理计算精确地算出了晶格点处原子间的相互作用，晶格蒙特卡罗模拟仍会高估有序-无序相变温度。在本文中，我们在对FePt合金的研究中处理这个问题，该合金最近因其磁性能而备受关注。我们应用一个简化版的势重整化理论来确定原子间的相互作用，借助第一性原理计算部分地纳入非晶格效应。然后，我们利用该相互作用在面心立方晶格上对FePt合金进行晶格蒙特卡罗模拟。从结果来看，我们发现经过当前重整化程序后得到的转变温度更接近实验值。
