Gourdon Olivier, Gout Delphine, Williams Darrick J, Proffen Thomas, Hobbs Sara, Miller Gordon J
Los Alamos National Laboratory, Los Alamos, New Mexico 87545, Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA.
Inorg Chem. 2007 Jan 8;46(1):251-60. doi: 10.1021/ic0616380.
The crystal structures, atomic distributions, and theoretical electronic structures of five different Cu5-xZn8+x gamma-brass compounds (x = -0.59(3), -0.31(3), 0.00(3), 0.44(3), and 0.79(3)) are reported with the goal of identifying chemical influences on the observed phase width. These structures have been refined by both neutron and X-ray powder diffraction to obtain accurate crystal chemical parameters. All compounds crystallize in the space group Iz3m (No. 217) (Z = 4), and the unit cell parameters are a = 8.8565(4), 8.8612(5), 8.8664(3), 8.8745(4), and 8.8829(7) A, respectively, for Cu5.59Zn7.41, Cu5.31Zn7.69, Cu5.00Zn8.00, Cu4.56Zn8.44, and Cu4.21Zn8.79. The results indicate specific site substitutions on both sides of the ideal composition "Cu5Zn8". In all cases, the 26-atom cluster building up the -brass structure shows a constant inner [Cu4Zn4] tetrahedral star with compositional variation occurring at the outer octahedron and cuboctahedron. First principles and semiempirical electronic structure calculations using both a COHP and Mulliken population analysis were performed to understand the observed compositional range and to address the "coloring problem" for the site preferences of Cu and Zn atoms for this series of compounds.
报道了五种不同的Cu5-xZn8+xγ-黄铜化合物（x = -0.59(3)、-0.31(3)、0.00(3)、0.44(3)和0.79(3)）的晶体结构、原子分布和理论电子结构，目的是确定对观察到的相宽度的化学影响。通过中子和X射线粉末衍射对这些结构进行了精修，以获得准确的晶体化学参数。所有化合物均结晶于空间群Iz3m（编号217）（Z = 4），对于Cu5.59Zn7.41、Cu5.31Zn7.69、Cu5.00Zn8.00、Cu4.56Zn8.44和Cu4.21Zn8.79，其晶胞参数分别为a = 8.8565(4)、8.8612(5)、8.8664(3)、8.8745(4)和8.8829(7) Å。结果表明在理想组成“Cu5Zn8”两侧存在特定的位点取代。在所有情况下，构成γ-黄铜结构的26原子簇显示出一个恒定的内部[Cu4Zn4]四面体星，组成变化发生在外部八面体和立方八面体。使用COHP和Mulliken布居分析进行了第一性原理和半经验电子结构计算，以理解观察到的组成范围，并解决该系列化合物中Cu和Zn原子位点偏好的“着色问题”。
