type: Hooke

references:
  - F.H. Featherston and J.R. Neighbours,
    Physical Review 130(4):1324-1333, 1963,
    https://doi.org/10.1103/PhysRev.130.1324,
    fit to Tab. II (T_min=100K, T_max=300K)

C_11: 523.6e+9
C_11,T: -7.704e+7
C_11,T^2: -1.562e+5

C_12: 204.6e+9
C_12,T: -2.485e+7
C_12,T^2: -1.182e+5

C_44: 160.7e+9
C_44,T: -1.028e+7
C_44,T^2: 1.291e+4

T_ref: 293.15