使用化物路径合成的化的晶体和电子结构
G W Chinthaka Silva1, Philippe F Weck, Eunja Kim
1Harry Reid Center for Environmental Studies, University of Nevada, Las Vegas, Box 454009, 4505 Maryland Parkway, Las Vegas, Nevada 89154, USA. silvagw@ornl.gov
Journal of the American Chemical Society
|January 28, 2012
概括
研究人员合成了氨酸单化物 (NpN),并发现了两种新的化物化合物,NpN(2) 和Np(2) Np(3). 这些发现扩展了已知的海王星化物系统,由DFT计算证实.
科学领域:
- 乙化物化学和材料科学
- 固态化学和结晶学
- 计算材料科学 计算材料科学
背景情况:
- mononitride (NpN) 是一个关键的动因化物化合物.
- 以前的研究仅集中在NpN上,因为缺乏其他化相的实验证据.
- 了解化系统对于核材料科学至关重要.
研究的目的:
- 使用低温化物路径合成海王星单化物 (NpN).
- 为了识别和表征新的化物种.
- 通过计算验证新发现的海王星化物晶体结构.
主要方法:
- 低温化物合成路径用于化.
- 用X射线结晶学测定NpN(2) 和Np(2) Np(3) 的结构.
- 密度函数理论 (DFT) 计算 (LDA+U,GGA+U) 用于确认晶体结构和研究电子性质.
主要成果:
- 在≤900°C的温度下成功合成了海星 mononitride (NpN).
- 鉴定和结构性表征两种新的化相:NpN(2) 和Np(2) Np(3).
- NpN(2) 呈现出面中心立方CaF(2) 型结构,Np(2) N(3) 采用体中心立方Mn(2) O(3) 型结构.
- 实验结果得到了DFT计算的证实,包括旋转轨道合效应.
结论:
- 低温化物路径对于合成海王星化物是有效的.
- 发现NpN2和Np2N3显著扩大了已知的化系统.
- 这项工作为这些新型化相的存在和结构提供了第一个实验和计算证据.
相关概念视频
02:42Ionic Crystal Structures
Ionic crystals consist of two or more different kinds of ions that usually have different sizes. The packing of these ions into a crystal structure is more complex than the packing of metal atoms that are the same size.
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
01:26Imperfections in Crystal Structure: Stoichiometric Point Defects
Schottky defects arise when some lattice points in a crystal, such as those in NaCl, remain unoccupied, creating lattice vacancies without disturbing the overall electrical neutrality of the crystal. This defect is common in ionic crystals where the positive and negative ions are similar in size, as seen in sodium chloride and cesium chloride. The presence of Schottky defects enables the crystal to conduct electricity to a small extent through an ionic mechanism. Electric fields cause nearby...
03:07Electron Affinity
The electron affinity (EA) is the energy change for adding an electron to a gaseous atom to form an anion (negative ion).
01:16Other Nuclides: 31P, 19F, 15N NMR
Many organic, inorganic, and biological molecules contain spin-half nuclei such as nitrogen-15, fluorine-19, and phosphorus-31. As a result, NMR studies of these nuclei have found extensive applications in chemical and biological research.
While fluorine-19 and phosphorous-31 have high natural abundances (100%) and positive gyromagnetic ratios, nitrogen-15 has a low natural abundance and a negative gyromagnetic ratio. However, nitrogen-15 is still preferred over nitrogen-14 (which has a high...
While fluorine-19 and phosphorous-31 have high natural abundances (100%) and positive gyromagnetic ratios, nitrogen-15 has a low natural abundance and a negative gyromagnetic ratio. However, nitrogen-15 is still preferred over nitrogen-14 (which has a high...
01:25Imperfections in Crystal Structure: Point, Line and Plane Defects
A perfect crystal, in theory, has a uniform structure with the same unit cell and lattice points throughout. However, any deviation from this periodic arrangement is known as an imperfection or defect. These defects can be categorized into three types: point, line, and plane defects.Point defects occur when there is a deviation from the ideal due to missing atoms, displaced atoms, or additional atoms. These imperfections might occur due to imperfect packing during crystallization or because of...