We have measured the temperature dependence of lattice parameters of the ti
tle salts from 300 down to 11 K by a four circle Xray diffractometer. It is
confirmed that the ND4Hg(SCN)(4) salt shows essentially the same anisotrop
ic contraction of the cia with the NH4Hg(SCN)(4) salt. The deuteration enha
nces the cia ratio by 0.3 % at low temperatures.