The System Si-Al-O-N at Extreme Pressures: A Synthetic and Computational Route to Novel Materials?

我们的主要目标将是在系统Si？Al？O？N中定位潜在的新的高密度相，特别是在子系统Si2N2O中。。.Al_2O_3和Si3N_4。。.Aln.为了提供坚实的基础，我们将在自己前期工作的基础上，利用多砧木技术合成大尺寸的-Si3N4和岩盐型AlN(rS-AlN)单晶。大晶体将使我们能够非常准确地表征物理性质(弹性性质、电子结构、振动光谱)，为理论结果提供严格的测试。然后将使用静态高压技术和冲击波合成技术来探索三元(Si？O？N)和四元(Si？Al？O？N)相的存在，以便生产更多的材料。产品将进行全面的表征，包括X射线、红外显微镜和显微拉曼光谱、分析高分辨率透射电子显微镜、电子探针、SIMS/SNMS和固体核磁共振。对这些体系的理论研究将基于第一性原理密度泛函理论计算。该项目将提供对高压和高温下Si？Al？O？N系统基本未知的相行为的基本见解。

Our main goal will be to locate potential new high density phases within the system Si¿Al¿O¿N in particular in the subsystems Si2N2O. . .Al2O3 and Si3N4. . .AlN. In order to provide a firm basis we will synthesise large single crystals of ¿-Si3N4 and rocksalt type AlN (rs-AlN) based on our own preliminary work using multi-anvil techniques. Large crystals will enable us to characterise physical properties (elastic properties, electronic structure, vibrational spectra) very accurately, providing a stringent test for theoretical results. Existence of ternary (Si¿O¿N) and quarternary (Si¿Al¿O¿N) phases will then be probed using static high pressure techniques supplemented by shock wave synthesis in order to produce larger amounts of material. The products will be subjected to thorough characterisation including X-ray, IR-microscopy and micro-Raman spectroscopy, analytical high resolution TEM, EPMA, SIMS/SNMS and solid state NMR. Theoretical investigations on these systems will be based on first-principles density-functional theory calculations. The project will provide fundamental insight into the largely unknown phase behaviour of the system Si¿Al¿O¿N at high pressures and high temperatures.