| With the development of quantum theory and computing technology and the advancement of computer performance, the research for the structure and characteristic of materials using computer-simulation technology develops widely. The inter-atomic potentials decide the microstructure and physical, chemical characteristics of systems and are the basis of all simulative calculations on atomic level.Ⅱ-Ⅵcompounds are used widely in the preparation of laser, infrared and piezoelectricity component etc because of wide gap and transition energy band structure. So it is very important to find a laconic and feasible potential function ofⅡ-Ⅵcompounds by calculation and fitting to do more MD simulation of quantum dots and clusters.In this work, first-principles method based on DFT and HF are used to calculate the two-body and three-body inter-atomic potentials ofⅡ-Ⅵcompounds CdS,CdSe,CdTe and HgTe. The calculation results are compared with experimental data. The influence of the basis sets to the results and the merit and dismerit of various approximate methods are analyzed. On the one hand, sinceⅡ-Ⅵcompounds usually have ionic and covalent property together, Lennard-Jones potential, Born-Mayer potential and Morse potential are used to fit the two-body potential energy curve. On the other hand, since angel must be considered in multi-bodies'interaction and the structures ofⅡ-Ⅵcompounds are similar to the structure of Si, SW potential is use to fit the three-body potential energy curve. We come to the following conclusions:①The interatomic potentials ofⅡ-Ⅵcompounds CdS, CdTe, CdTe, HgTe were calculated by first-principles method and compared with the experimental data. The results of calculation are trustiness.②Two-body potentials ofⅡ-Ⅵcompounds are fitted. The results show that potential curve fitted by Morse potential is the best, so Morse potential applied in covalent molecules is also suitable for II-VI compounds.③In the two-body potentials'calculation ofⅡ-Ⅵcompounds, electron correlation considered in DFT, so the results calculated by B3LYP and LDA based on DFT are better than results calculated by HF. Some pseudo-potential basis sets which calculate ECP and relativistic effect should be used when calculate some weight atoms to expedite the calculation and the result calculated by the method is good.④The three-body potentials ofⅡ-Ⅵcompounds are calculated, compared and analyzed. Stilling-Weber (SW) potential is used to fit the three-body potentials ofⅡ-Ⅵcompounds. If the angle is invariable, the proportion of three-body part in total potential is increased with the increase of distance when the distance ofⅡ,Ⅵfamily atoms is short and the proportion is the largest when the potential of repulsion close to the potential of attraction. If the distance increase continued, the proportion of three-body part in total potential will descending with the increase of distance.⑤If the distance ofⅡ,Ⅵfamily atoms is invariable, the proportion of three-body part in total potential is increased with the increase of angle when the angel is small and the proportion increase to the largest when the angle in the range of 90 o~ 120 o.After that, the proportion descending with the increase of angle. Since the bond angle of Zinc-blende structure is 109 o28′, the effect of three-body part to the total potential ofⅡ-Ⅵcompounds crystal is great.⑥Since the effects of angles are considered in SW potential, it can describe the three-body potentials very well. SW potential can be try to used in Molecular Dynamics Simulations ofⅡ-Ⅵquantum dots, cluster.Although some of our results still need to be modified by experiments, they have some certain directive purport and reference worth on further investigation of the multi-body potential ofⅡ-Ⅵcompounds.
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