[gmx-users] Error with dihedral type 5

[Matteo Busato]

Hi to everyone,

I was trying to perform a dynamics about the DG of solvation of a molecule in an ionic liquid described by the Lopes-Padua force field, however the dihedrals in that ff are described with function n. 5 and gromacs gave me the error: "Function type Fourier Dih. not implemented in ip_pert". I know this happens just with decoupling (in fact it gives me no error when there's no decoupling in the .mdp) and I've already read the message be Vitaly Chaban in the mail list. However, I've not understood some things:


- Why do I get an error about the dihedrals if the decoupling is just for intermolecular (wdv + q) interactions and in the .mdp file "couple-intramol" is set to "no"?

- Is there a way to convert dihedral type 5 to dihedral type 2? I couldn't find this in the manual.


I'll post here the .mdp part regarding the decoupling:


; Free energy control stuff
free_energy              = yes
init_lambda_state        = 0
delta_lambda             = 0
calc_lambda_neighbors    = 1        ; only immediate neighboring windows
; Vectors of lambda specified here
; Each combination is an index that is retrieved from init_lambda_state for each simulation
; init_lambda_state        0    1    2    3    4    5    6    7    8    9    10   11   12   13   14   15   16   17   18   19   20
vdw_lambdas              = 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
coul_lambdas             = 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
; We are not transforming any bonded or restrained interactions
bonded_lambdas           = 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
restraint_lambdas        = 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
; Masses are not changing (particle identities are the same at lambda = 0 and lambda = 1)
mass_lambdas             = 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
; Not doing simulated temperting here
temperature_lambdas      = 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
; Options for the decoupling
sc-alpha                 = 0.5
sc-coul                  = no       ; linear interpolation of Coulomb (none in this case)
sc-power                 = 1.0
sc-sigma                 = 0.3
couple-moltype           = zn       ; name of moleculetype to decouple
couple-lambda0           = none     ; no interactions at lambda=0
couple-lambda1           = vdw-q    ; turn on both vdW and Coulomb
couple-intramol          = no
nstdhdl                  = 10


Thank you in advance.

Kind regards, Matteo Busato