FePt纳米合金的振动性质和稳定性
Vibrational properties and stability of FePt nanoalloys
摘要：
采用密度泛函理论研究了FePt纳米粒子的结构和动力学性质。研究了立方八面体和二十面体对称纳米粒子的尺寸和化学组成对动力学稳定性的影响。在立方八面体中，观察到的结构畸变，这对于奇数Pt层的系统导致降低的四面体对称性。观察到FePt颗粒和大块晶体的振动性质之间的显着差异，但类似于FePt晶体，立方八面体颗粒表现出很强的原子振动的各向异性。具有完美壳层几何形状的二十面体颗粒由于Fe原子之间的距离增大而不稳定。它们可以通过去除中心原子或用更小的原子取代来稳定。纳米颗粒的热容和熵表现出典型的增强，由于在表面层的低能振动。
英文摘要：
The structural and dynamical properties of FePt nanoparticles were studied within the density functional theory. The effect of size and chemical composition on dynamical stability of nanoparticles was investigated for the cuboctahedral and icosahedral symmetries. In cuboctahedra, the structural distortion is observed, which for systems with odd number of Pt layers leads to lowering of the tetragonal symmetry. Significant differences between the vibrational properties of FePt particles and bulk crystal is observed, but similarly to the FePt crystal, cuboctahedral particles exhibit a strong anisotropy of atomic vibrations. The icosahedral particles with perfect shell geometry are unstable due to enlarged distances between Fe atoms. They can be stabilized by removing a central atom or replacing it by a smaller one. The heat capacity and entropy of nanoparticles show typical enhancement due to low-energy vibrations at the surface layers.
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