Molecular Dynamics Simulation Of Dynamic Properties On The Low Index Ordered B2-FeAl Surfaces

In the present thesis, using the analytic embedded atom method (EAM) and molecular dynamics(MD), the surface dynamic properties, such as atomic vibrations, anharmonicity and vibrational properties of adatoms for B2-FeAl are studied carefully.Firstly, some basic concepts of surfaces have been briefly summarized. The analytic embedded atom method and molecular dynamics are also introduced.In the third chapter, the anharmonic effects on B2-FeAl (110) surface are studied in the temperature range from 0 K to 1400 K. In order to confirm the reliability the potential, the bulk melting point, bulk phonon density of states (DOS), surface energies for B2-FeAl are calculated, which are in reasonable agreement with experimental data and ab initio calculations. The temperature dependences of the interlayer spacing, mean square vibrational amplitudes, surface phonon frequencies and line-widths, and layer structure factor have been calculated. The obtained results indicate that the anharmonic effects are small in the temperature range from 0 K to 900 K. The temperature dependences of the interlayer spacing indicates that the rippling effect of the B2-FeAl(110) surface is exhibited by the contraction of Fe surface atoms and the expansion of Al atoms, which persists at high temperatures. The temperature dependence of the layer structure factors shows that the B2-FeAl(110) surface does not disorder until the temperature of 1300 K.In the fourth chapter, the anharmonic effects are studied on B2-FeAl (001) and B2-FeAl (111) surfaces. The temperature dependences of the interlayer spacing, mean square vibrational amplitudes, surface phonon frequencies and line-widths, and layer structure factor have been also studied. The results show that the anharmonic effects are small up to 700 K on B2-FeAl (001) and 500 K on B2-FeAl (111). In addition, relative order of anarmonic intensity for the low-index B2-FeAl sufaces is obtained( namely B2-FeAl (111)