Calcium titanite CaTiSiO5 undergoes a phase transition at similar to 220 de
grees C. Extended X-ray Absorption Fine Structure (EXAFS) spectra of both c
alcium and titanium K-edge have been collected and local structural informa
tion extracted from them. The results have been compared with the existing
XRD data on this material and the agreement is excellent. In particular, th
ere is good agreement on the changes in bond lengths that occur at the phas
e transition. A complementary computer simulation study has also been perfo
rmed and defect formation energies have been calculated.