cell_dyn -cell dynamics control variable

DESCRIPTION

The cell_dyn variable determines the algorithm used to update the cell dimensions during a molecular dynamics simulation. The following values are allowed:
 

LOCKED: The cell dimensions are fixed. The stress tensor is not calculated.

 

SD: Steepest Descent. The cell dimensions are updated using a steepest descent algorithm:

    a_x(t) = a_x(t-dt) + stress_x * dt² / vmass

where a_x(t) is the cell dimension in the x direction, and vmass is the mass associated with the cell degrees of freedom.
 

MD: Molecular Dynamics. The cell dimensions are updated using a Verlet algorithm:

    a_x(t) = 2 * a_x(t) - a_x(t-dt) + stress_x * dt² / vmass

If the vdamp variable is non-zero, a damping term is added to the Verlet algorithm as follows:

    a_x(t) = a_x(t) + (1-vdamp) * (a_x(t)-a_x(t-dt)) + stress_x * dt² / vmass
 
 

BMD: Blocking Molecular Dynamics. The cell dimensions are updated using the Verlet algorithm (with damping if vdamp > 0). The cell velocities are set to zero whenever the total energy is increasing.

ALLOWED VALUES

LOCKED, SD, MD, BMD
 

vmass, vdamp, stress