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采用平均场近似方法对两组元面心立方合金薄膜的有序无序相转变过程进行模拟计算,结果表明,合金薄膜的有序无序相变受薄膜层数奇偶性的影响.薄膜层数奇偶性不同,会导致薄膜具有不同的相结构和热力学性质.在弱表面偏析作用下,对于偶数层薄膜,由于薄膜边界对称性破缺,对应体组分x=0·5的化学势区间,偶数层薄膜有序无序相变过程中出现了中间温度相和浸润现象.而奇数层薄膜的有序无序相变类似体材料的相变.在强表面偏析作用下,由于受表面偏析作用和有限尺寸效应影响,对应体组分x=0·5的化学势区间,奇数层薄膜中出现AB(AB)nA相,它不存在严格热力学意义上的有序无序相变.
The average field approximation method was used to simulate the ordered disorder phase transformation of the two groups of elemental face-centered cubic alloy films. The results show that the ordered disorder transition of the alloy thin films is affected by the parity of the film layers. Different polarities lead to different phase structure and thermodynamic properties of thin films.With the weak surface segregation, due to the symmetry of the thin film boundaries being broken even for the even layers, the chemical potential corresponding to the body composition x = 0.5, In the orderly and disorderly phase transition of even-numbered films, the intermediate temperature phase and the infiltration phenomenon appear, while the phase change of the ordered materials in the odd-numbered films is similar to that of the bulk materials. Under the effect of surface segregation, And the finite size effect, AB (AB) nA appears in the odd-layer thin film due to the chemical potential region corresponding to the body composition x = 0.5. There is no strict thermodynamic orderly disorder phase transition.