The atomic motions in crystals are correlated. In this paper we demonstrate that information about the correlated motion of atoms, and consequently about the bonding within the crystal, can be obtained by analyzing the peak width of the atomic pair distribution function (PDF). We have measured the PDFs of Ni and InAs using synchrotron X-ray diffraction. The analysis of the Ni data allowed us to determine the Debye temperature which is in good agreement with values found in the literature. In contrast to the isotropic metallic bonding in Ni resulting in a relatively weak correlation between the motion of neighboring atoms, we found a very strong correlation in InAs as one might expect from the covalent bond between In and As. The results are compared with theoretical predictions by Chung and Thorpe (Phys. Rev. B 1977, 55, 1545).

Nearest and higher neighbor distances as well as bond length distributions (static and thermal) of the InxGa1−xAs (0 ≤ x ≤ 1) semiconductor alloys have been obtained from high real-space resolution atomic pair distribution functions (PDFs). Using this structural information, we modeled the local atomic displacements in InxGa1−xAs alloys. From a supercell model based on the Kirkwood potential, we obtained 3-D As and (In,Ga) ensemble averaged probability distributions. This clearly shows that As atom displacements are highly directional and can be represented as a combination of 100 and 111 displacements. Examination of the Kirkwood model indicates that the standard deviation (σ) of the static disorder on the (In,Ga) sublattice is around 60% of the value on the As sublattice and the (In,Ga) atomic displacements are much more isotropic than those on the As sublattice. The single crystal diffuse scattering calculated from the Kirkwood model shows that atomic displacements are most strongly correlated along 110 directions. 61.72.Dd,61.43.Dq,61.43.Bn,61.12.Ld

High resolution total and indium differential atomic pair distribution functions (PDFs) for In0.5Ga0.5As alloys have been obtained by high energy and anomalous x-ray diffraction experiments, respectively. The first peak in the total PDF is resolved as a doublet due to the presence of two distinct bond lengths, In-As and Ga-As. The In differential PDF, which involves only atomic pairs containing In, yields chemical specific information and helps ease the structure data interpretation. Both PDFs have been fit with structure models and the way in that the underlying cubic zinc-blende lattice of In0.5Ga0.5As semiconductor alloy distorts locally to accommodate the distinct In-As and Ga-As bond lengths present has been quantified.

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