Investigations into the Phase Segregation, Formation of nanostructure with a high thermal stability and origin of the hardness enhancement in Superhard Nanocomposites consisting of a stable, hard, transition metal nitride and Si3N4 or BN as interfacial ph

Ti-Si-N、Ti-B-N、Ti-Al-N、Cr-Al-N等氮化物体系形成超硬纳米复合材料和涂层的相稳定性和偏析的理论研究。从头算DFT计算将提供亚稳相的晶格稳定性和相互作用参数，这些参数将用于计算与纳米复合材料的沉积和应用相关的大范围氮压力和温度下混合化学计量氮化物的吉布斯自由能。如果，如预期的那样，这些计算将产生化学旋量，将考虑界面能的影响，以阐明是否，以及在何种条件下，系统将保持相干旋量。稍后，计算将扩展到更复杂的系统，如nc-(TiAl)N/a- Si3N4, nc-(AlCr)N/a-Si3N4，如果时间允许，还可以选择对工业应用有很大兴趣的氧化物系统。通过计算TiN、Si3N4、Si3N4等纯物质的材料参数来检验结果的可靠性。（形成能、晶格常数、弹性模量、退聚能），并与现有实验数据进行比较。为了了解硬度增强的原因，将采用从头算DFT方法计算应变-应力曲线，并将其用于构建纳米复合材料和新近制备的异质结构的真实力学模型。

Theoretical investigation into the phase stability and segregation in nitride systems, such as Ti-Si-N and Ti-B-N, Ti-Al-N, Cr-Al-N, which form superhard nanocomposites and coatings. Ab initio DFT calculations will provide the lattice stability of metastable phases and the interaction parameters which will be used to calculate the Gibbs free energy of the mixed stoichiometric nitrides in wide range of nitrogen pressure and temperature that are relevant for the deposition and application of the nanocomposites. If, as expected, these calculations will yield the chemical spinodal, the effect of the interfacial energy will be considered in order to elucidate if, and under which conditions the system will remain also coherently spinodal. Later on, the calculations will be extended to more complex systems, such as nc-(TiAl)N/a- Si3N4, nc-(AlCr)N/a-Si3N4, and - if the time will allow us - also to selected oxide systems which may be of great interests for industrial applications. The reliability of the results will be tested by calculating the materials parameters for pure substances, such as TiN, Si3N4 ... (energy of formation, lattice constant, elastic moduli, decohesion energy) and their comparison with available experimental data. In order to understand the origin of the hardness enhancement, the strain - stress curves will be calculated using the ab initio DFT method, and than used in a construction of realistic mechanical models of both, the nanocomposites and of the recently prepared heterostructures.