[gmx-users] normal mode analysis

[Nguyen Hoang Phuong]

Dear All,

I would like to perform the NMA for my peptide using GROMACS. First, the
energy minimization is performed by using the conjugate gradient method
and I got the maximum force:  5.87485e-02. Second, the program nmrun is
run and the maximum force is 4.21849e+02. I got the negative values 
of the frequencies after the diagonalization of the Hessian.

My question is that why the later maximum force is much higher than the
first one? Thanks for any explaination.

Phuong