面心立方金属对称和非对称方向的声子谱

The phonon dispersion of FCC metals in symmetry and off-symmetry directions

依据晶格动力学理论,采用改进分析型嵌入原子法(Modified Analytic Embedded AtomMethod,MAEAM),沿Brillouin区中的4个对称方向和4个非对称方向,计算了面心立方金属Al、Ni、Rh、Ir、Pd、Pt、Pb的声子谱.结果表明,除Rh、Ir和Pb误差稍大外,其余理论计算结果与实验符合很好,预示着非对称方向计算值的正确性.同时表明MAEAM能够用来描述面心立方(FaceCenter Cubic,FCC)金属晶体原子间的多体相互作用,但是还需要改进和提高.沿着相同方向,FCC金属的声子谱曲线相似,频率依次沿Al、Ni、Rh、Ir、Pd、Pt、Pb的顺序降低,这是由于它们的原子质量与结合能的比值依次降低的缘故.

Combining the modified analytic embedded atom method（MAEAM） with the theory of lattice dynamics,the phonon dispersion curves along four symmetry and four off-symmetry directions are calculated.The results showed that the phonon dispersion curves are in good agreement with the available experimental data except for that of Rh,Ir and Pb,which implies that the predicted phonon dispersion along off-symmetry directions are well behaved.It is further proved that the MAEAM gives a good description of many-body interatomic interactions in FCC metals.For seven FCC metals,the phonon frequency decreases for Al、Ni、Rh、Ir、Pd、Pt and Pb successively due to the ratio of the cohesion energy to the atom mass decreases.