  We report the structural parameters of superconducting MgCxNi3 (x=0.96,
TC=7.3 K) as a function of temperature, from 2 K to 295 K, determined by
neutron powder diffraction profile refinement. The compound has the perovskite
structure over the whole temperature range, with symmetry Pm3m and a=3.81221(5)
A at 295 K: no structural or long range magnetic ordering transitions were
observed. The lattice parameter a and the Debye-Waller factors for the
individual atoms decrease smoothly with decreasing temperature. There are no
unusual changes of the structural parameters near TC.
