vdamp -damping parameter for cell dynamics
The vdamp variable determines the amount of damping included in the dynamics of the unit cell. It is used only if cell_dyn is set to MD or BMD, and ignored otherwise. A value of 0 is equivalent to no damping. A value of 1 is equivalent to Steepest Descent (cell_dyn=SD). Positive values in [0,1] cause energy to be dissipated in the cell dynamics.