Investigation of the structure of beta-Tantalum
  The local structure of beta-tantalum was investigated by comparing experimental extended x-ray absorption fine structure (EXAFS) measurements with calculated spectra of proposed models. Four possible structure candidates were examined: a beta-Uranium based structure, a distorted A15 structure, a bcc-Ta based superlattice structure with N interstitials and a simple hcp structure. The local structural measurements were found to be consistent with the beta-Uranium based model containing 30 atoms per unit cell and having the space group P42/mnm. The thermal effect analysis on x-ray diffraction and EXAFS spectra, which reveals that beta-Ta is highly disordered, agrees with the low symmetry and anisotropic system of the beta-U model. 
Aiqin Jiang, Anto Yohannan, Neme O. Nnolim, Trevor A. Tyson, Lisa Axe,   Sabrina L. Lee and Paul Cote