Low temperature specific heats and related thermodynamical functions of neodymium dihydride NdH2.00. crystal field effects

The heat capacity of neodymium dihydride NdH2.00 was measured over the low‐temperature range by adiabatic calorimetry. At 298.15 K the measured heat capacity at constant pressure (Cp), the entropy (S0), the enthalpy function (H0–H ), and the Gibbs function–[(F0–H )/T] are: 10.29 cal mol−1 deg−1, 14.08 cal mol−1 deg−1, 1882 cal mol−1, and 7.76 cal mol−1 deg−1, respectively. The influence of the crystal field of cubic symmetry on the splitting of the ground level 4I9/2 of the Nd3+ ion was analysed, and the conclusion was drawn that the quartet Γ is the lowest‐lying level. This supports the idea of the anion‐like character (hydridic model) of hydrogen in this hydride.