The Crystal Lattice of Germano Sulphide, GeS

Abstract

The crystal lattice of germano sulphide, GeS, was examined by means of the Laue method, the powder method and the oscillating crystal method. The crystals are orthorhombic bipyramidal. The dimensions of the unit cell were found to be: $a=4.29\ifmmode\pm\else\textpm\fi{}0.01\mathrm{A}$, $b=10.42\ifmmode\pm\else\textpm\fi{}0.03\mathrm{A}$, $c=3.64\ifmmode\pm\else\textpm\fi{}0.01\mathrm{A}$. There are four molecules GeS in the unit cell and the calculated density is 4.24. The space group is $\mathrm{Pb}\mathrm{nm}({{V}_{h}}^{16})$. The germanium atoms as well as the sulphur atoms are lying in the reflection planes: $(\mathrm{uv}0)(\overline{u}, \frac{1}{2}\ensuremath{-}v, \frac{1}{2})(u+\frac{1}{2}, \overline{v}, \frac{1}{2})(\frac{1}{2}\ensuremath{-}u, v+\frac{1}{2}, 0)$. The values of the four parameters, ${u}_{1}{v}_{1}$ for Ge and ${u}_{2}{v}_{2}$ for $S$, were determined on the basis of intensity calculations, the final result being: ${u}_{1}=0.167 (60\ifmmode^\circ\else\textdegree\fi{})$, ${u}_{2}=0.111 (40\ifmmode^\circ\else\textdegree\fi{})$, ${b}_{1}=\ensuremath{-}0.125 (\ensuremath{-}45\ifmmode^\circ\else\textdegree\fi{})$, ${v}_{2}=0.111(40\ifmmode^\circ\else\textdegree\fi{})$. The crystal structure can be described as a deformed rocksalt lattice, the deformation being very great in the direction of the $a$ axis. The germanium atoms are surrounded by distorted octahedra formed by sulphur atoms. The germanium atom is not lying at the center of the octahedron, but is displaced towards one of the octahedral faces. The distance from germanium to three of the sulphur atoms in this manner is distinctly smaller than to the three others. The two distances Ge-S are: 2.58A (average of 2.47, 2.64, 2.64) and 2.97A (average of 2.91, 3.00, 3.00). The closest approach between two sulphur atoms is 3.55A.