Ruiping Liu

Theoretical calculation of the dislocation width and Peierls barrier and stress for semiconductor silicon

The dislocation width and Peierls barrier and stress have been calculated by the improved Peierls-Nabarro (PN) theory for silicon. In order to investigate the discreteness correction of a complex lattice quantitatively, a simple dynamics model has been used in which interaction attributed to a variation of bond length and angle has been considered. The results show that the dislocation core and mobility will be corrected significantly by the discrete effect. Another improvement is considering the contribution of strain energy in evaluating the dislocation energy. When a dislocation moves, both strain and misfit energies change periodically. Their amplitudes are of the same order, but phases are opposite. Because of the opposite phases, the misfit and strain energies cancel each other and the resulting Peierls barrier is much smaller than that given by the misfit energy conventionally. Due to competition between the misfit and strain energies, a metastable state appears separately for glide 90° and shuffle screw dislocations. In addition, from the total energy calculation it is found that besides the width of dislocation, the core of a free stable dislocation may be different according to where the core center is located. The exact position of the core center can be directly verified by numerical simulation, and provides a new prediction that can be used to verify the validity of PN theory. It is interesting that after considering discrete correction the Peierls stress for glide dislocation coincides with the critical stress at low temperature, and the Peierls stress for shuffle dislocation coincides with the critical stress at high temperature. The physical implication of the results is discussed.

The discrete correction of the core structure for the \langle 100\rangle \{010\} edge dislocation in bcc Fe

The core structure of the edge dislocations in body-centered cubic (bcc) crystal Fe has been investigated by the modified Peierls–Nabarro (P–N) equation which includes the discrete correction. An analytical expression of the dislocation solution of the dislocation equation has been obtained by using the truncation approximation. It is found that the dislocation width is nearly doubled by the discrete effects and the agreement between the theoretical prediction and the numerical simulation is improved remarkably.

The Peierls stress of the moving \frac {1}{2}\langle 111\rangle \{110\} screw dislocation in Ta

The Peierls stress of the moving [Formula: see text] screw dislocation with a planar and non-dissociated core structure in Ta has been calculated. The elastic strain energy which is associated with the discrete effect of the lattice and ignored in classical Peierls-Nabarro (P-N) theory has been taken into account in calculating the Peierls stress, and it can make the Peierls stress become smaller. The Peierls stress we obtain is very close to the experimental data. As shown in the numerical calculations and atomistic simulations, the core structure of the screw dislocation undergoes significant changes under the explicit stress before the screw dislocation moves. Moreover, the mechanism of the screw dislocation is revealed by our results and the experimental data that the screw dislocation retracts its extension in three {110} planes and transforms its dissociated core structure into a planar configuration. Therefore, the core structure of the moving [Formula: see text] screw dislocation in Ta is proposed to be planar.

The Peierls stress of the moving screw dislocation in Ta

The Peierls stress of the moving [Formula: see text] screw dislocation with a planar and non-dissociated core structure in Ta has been calculated. The elastic strain energy which is associated with the discrete effect of the lattice and ignored in classical Peierls-Nabarro (P-N) theory has been taken into account in calculating the Peierls stress, and it can make the Peierls stress become smaller. The Peierls stress we obtain is very close to the experimental data. As shown in the numerical calculations and atomistic simulations, the core structure of the screw dislocation undergoes significant changes under the explicit stress before the screw dislocation moves. Moreover, the mechanism of the screw dislocation is revealed by our results and the experimental data that the screw dislocation retracts its extension in three {110} planes and transforms its dissociated core structure into a planar configuration. Therefore, the core structure of the moving [Formula: see text] screw dislocation in Ta is proposed to be planar.

The Peierls stress of the moving [Formula: see text] screw dislocation in Ta.

The Peierls stress of the moving [Formula: see text] screw dislocation with a planar and non-dissociated core structure in Ta has been calculated. The elastic strain energy which is associated with the discrete effect of the lattice and ignored in classical Peierls-Nabarro (P-N) theory has been taken into account in calculating the Peierls stress, and it can make the Peierls stress become smaller. The Peierls stress we obtain is very close to the experimental data. As shown in the numerical calculations and atomistic simulations, the core structure of the screw dislocation undergoes significant changes under the explicit stress before the screw dislocation moves. Moreover, the mechanism of the screw dislocation is revealed by our results and the experimental data that the screw dislocation retracts its extension in three {110} planes and transforms its dissociated core structure into a planar configuration. Therefore, the core structure of the moving [Formula: see text] screw dislocation in Ta is proposed to be planar.