Beddi, Abdelkader2019-04-252019-04-252018-06-28salle des thesesMS-530-70-01https://dspace.univ-tlemcen.dz/handle/112/14120Using an ab initio calculation, we show in this work that we can easily simulate the reconstructive phase transition mechanism B3B1 generated by the application of a hydrostatic pressure to binary compounds. We use an intermediate state (Imm2) with orthorhombic form. We have relied the parent phases by means of a groupsubgroup relationship. The choice of sub-group is not born by chance but through the computation of local constraints along the transformation path. The intermediate phase Imm2 has been simulated in the binary by a sol coordinate at the z position of the cation. The transition path generates a decrease in the volume due to the change of the two structural ratios c /a and b/ a. The tolerance parameter of the deformation being minimal; the phase transition of both binaries compounds need a minimum activation energy. The curve of the transition path gave a smooth and well symmetrical shape. Our activation barriers, calculated using the martensitic approach, show that the ionic CuBr needs a very small energy to undergoes from the semiconductor state to the metallic state (B1). Whereas, the GaAs compound, requires 10 times more energy to undergoes this transition.frab initio - mécanisme microscopique - transitions reconstructives - binaires de type B3Thesis