8Grains:
N_constituents: 8
mechanical:
type: RGC
D_alpha: [4.0e-06, 4.0e-06, 2.0e-06]
a_g: [0.0, 0.0, 0.0]
c_alpha: 2.0
cluster_size: [2, 2, 2]
output: [M, Delta_V, avg_a_dot, max_a_dot]
xi_alpha: 10.0