[gmx-users] second derivative of force

[Nguyen Hoang Phuong]

Dear All,

I would like to obtain the second derivative of the total force 
d^2f_i/dr_i^2 at every atom i along the trajectory. In principle, this can be
obtained from the Hessian matrix. However, I don't need the cross terms like 
d^2f_i/dr_i dr_j, therefore it will be very time consumming to calculate
the Hessian matrix along the trajectory if I just need the off-diagonal 
terms. Does anyone know a way to do that? Thanks.

Phuong