Ti-Si-N结构及热力学性质的第一性原理研究

First-principles Study on Structure and Thermodynamic Properties of Ti-Si-N

采用基于密度泛函理论的平面波赝势方法,研究了具有置换型界面的Ti-Si-N的结构、弹性常数及热力学性质。在计算热力学性质时,先计算一组不同晶格常数下的Ti-Si-N的声子谱及相应的静态总能,由此得到不同晶格常数下的自由能;再由准谐近似及自由能极小判据得到自由能与温度的关系,进而计算热膨胀系数、定容摩尔热容及定压摩尔热容与温度的关系。计算结果说明制备Ti-Si-N及类似薄膜时,要选择合适的基底、温度等条件。

The structures, elastic constants and thermodynamic properties of substitutional interface Ti-Si-N were studied with the aid of plane wave pseudopotential method based on density functional theory. When calculating thermodynamic properties, the phonon spectrum and the corresponding static total energy were calculated for a different set of lattice constants of Ti-Si-N, then the free energy was obtained with different lattice constants. The temperature dependence of free energy was achieved by quasi-harmonic approximation and minimization criterion of free energy, and further the temperature dependences of coefficient of thermal expansion, constant volume molar heat capacity and constant pressure molar heat capacity with temperatures were calculated. It is indicated that the selections of appropriate substrate, temperature and other conditions are necessary when preparing Ti-Si-N and similar thin films.