type: Hooke

references:
  - W.C. Overton Jr. and J. Gaffney,
    Physical Review 98(4):969-977, 1955,
    https://doi.org/10.1103/PhysRev.98.969,
    fit to Tab. I (T_min=100K, T_max=300K)
  - Y.A. Chang and L. Himmel,
    Journal of Applied Physics 37:3567-3572, 1966,
    https://doi.org/10.1063/1.1708903,
    fit to Tab. II (T_min=300K, T_max=800K)

C_11: 168.9e+9
C_11,T: -3.332e+7
C_11,T^2: -1.074e+4

C_12: 121.8e+9
C_12,T: -1.402e+7
C_12,T^2: -9.003e+3

C_44: 75.8e+9
C_44,T: -2.555e+7
C_44,T^2: -2.188e+3

T_ref: 293.15