[CP2K:1887] Geometry optimization convergence problem

[Teodoro Laino]

Dear Peter,

You have 13K atoms and roughly 40K DOFs. Moreover the optimizer work in 
cartesian coordinates (which is
possibly the worst choice for efficient optimizations).
Achieving the threshold you mentioned may become a real issue (if you 
could succeed at all).

The limit you have reached of 2e-3 Hartree/bohr is not bad at all (is in 
the order of ~ 3 kcal/angstrom).
If you really want to freeze up to 1e-4 Hartree/bohr the only way to 
efficiently get it (using cartesian coordinates)
is an annealed MD. Start with temperature 0 and put an annealing of 
0.99-0.97.
Again.. don't expect too much with so many degrees of freedom.
Cheers
Teo

Peter wrote:
> Dear all,
>
> I'm trying to optimize geometry of a large (~13000 atoms, it's a
> protein) mechanical (FIST using charmm27 FF) isolated system.
> Unfortunately both CG and LBFGS fails to converge to reasonable values
> of maximum gradient (4.5E-4 Hartree/Bohr). After approximately 1e3
> steps, maximum gradient value starts to oscillate around 2e-3 and
> leaves no hope for convergence (see fig.
> http://groups.google.com/group/cp2k/web/max_grad_vs_step.gif).
>
> How could I tune either of the algorithms to achieve convergence?
>
> I've uploaded archive with my input, structure and FF parameters files
> here:
> http://groups.google.com/group/cp2k/web/geo_opt-no_convergence.tar.gz
>
> Thanks in advance,
> Peter
>
> P.S. Here are the contents of one of the input files (LBFGS), so that
> you needn't to untar the archive to take a look at it:
>
> &GLOBAL
>   PROJECT OPT-LBFGS
>   RUN_TYPE GEO_OPT
>   PREFERRED_FFT_LIBRARY FFTMKL
> &END GLOBAL
>
> &MOTION
>   &GEO_OPT
>     TYPE MINIMIZATION
>     MAX_ITER 20000
>     OPTIMIZER LBFGS
>     &LBFGS
>       MAX_H_RANK 10
>       MAX_F_PER_ITER 100
>     &END LBFGS
>   &END GEO_OPT
>
>   &PRINT
>     &TRAJECTORY
>       FORMAT XYZ
>       FILENAME =lbfgs_opt.xyz
>     &END TRAJECTORY
>   &END PRINT
> &END MOTION
>
> &FORCE_EVAL
>   METHOD FIST
>   &MM
>     &FORCEFIELD
>       PARM_FILE_NAME par_all27_prot_lipid.prm
>       PARMTYPE CHM
>     &END FORCEFIELD
>
>     &POISSON
>       PERIODIC NONE
>       PSOLVER WAVELET
>       &EWALD
>         EWALD_TYPE NONE
>       &END EWALD
>     &END POISSON
>
>     &NEIGHBOR_LISTS
>       GEO_CHECK F
>     &END NEIGHBOR_LISTS
>   &END MM
>
>   &SUBSYS
>     &CELL
>       ABC 100 100 100
>       PERIODIC NONE
>     &END CELL
>
>     &TOPOLOGY
>       COORD_FILE_NAME 1AIG-apo_fe_uq_wat.pdb
>       COORD_FILE_FORMAT PDB
>       CONN_FILE_NAME 1AIG-apo_fe_uq_wat.psf
>       CONN_FILE_FORMAT PSF
>       CENTER_COORDINATES
>     &END TOPOLOGY
>   &END SUBSYS
> &END FORCE_EVAL
>
>
> >
>