X-ray Analysis of the Charge Density Distribution in GaP at 296 and 200 K Using a Multipole Model and the Maximum Entropy Method

From X-ray diffraction data sets the experimental electron density distribution and its derived properties in gallium phosphide at 296 and 200 K are derived and analyzed using an aspherical atom based multipole model refinement and the Maximum entropy method (MEM). The multipole analysis is done for the refinement of the population parameters. The topology of the charge density is analysed and the critical points in the charge density are determined. The effect of the temperature can be seen from the static and dynamic deformation maps. The covalent nature of the bonding is revealed in the 3-dimensional and 2-dimensional MEM maps and also from the one-dimensional electron density profiles. The quantitative analysis of the bonding is done using the charge density profiles along the bond path. The mid-bond density along the bonding direction is found to be around 0.67 e/angstrom(3) at 1.177 angstrom for both the RT and 200 K data sets. The strength of the covalency is found to be unaffected by the low temperature environment. The charge gathering at the respective atomic sites resulting from the low temperature environment is seen from the 3-dimensional and 2-dimensional maps and is supported by the evaluated overall and individual Debye-Waller factors. The charge integration around the atoms considered as spheres with covalent radii estimates the charge contributed by both the atoms for the bonding to be 4.272e(-), and this leads to the effective charge transfer from Ga to P as 0.5078 e(-).