[gmx-users] Relative binding free energy
Stefania Evoli
stefania.evoli at kaust.edu.sa
Mon Mar 14 09:40:48 CET 2016
Dear Users,
I’m performing relative binding free energy by using Gromacs 5.0.5. As I understood reading the sections 5.3.4, 6.1 and 7.3.23 of the GROMACS 5.0.5 manual I should avoid to use couple-moltype and couple-lambda0/couple-lambda1 because they would override the A and B states, already defined in the topology file. For this reason I put couple-lambda0 = none, couple-lambda1 = none and couple-intramol = yes to specify I want to modify intramolecular interactions. The problem I’m having regards the couple-moltype. If I don’t use it in the mdp file the minimization crashes and if I try to use couple-moltype=none I have the error ‘no such a molecule named none’ (as expected because this parameter is referred to the [moleculetype] section). Could someone that has more experience in this field than me give a look to my mdp file and help me to solve this problem, please.
Thank you!
NB the following mdp file is an example of my minimization mdp files for lambda=0
; RUN CONTROL PARAMETERS
integrator = steep
; Start time and timestep in ps
tinit = 0
dt = 0.002
nsteps = 2500
; mode for center of mass motion removal
comm-mode = Linear
; number of steps for center of mass motion removal
nstcomm = 100 ; must be equal or larger than calcenergy
nstcalcenergy = 100 ; Default
; CUTOFF SCHEME (default = verlet now)
cutoff-scheme = group
; ENERGY MINIMIZATION OPTIONS
; Force tolerance and initial step-size
emtol = 100
emstep = 0.01
; Max number of iterations in relax_shells
niter = 20
; Step size (1/ps^2) for minimization of flexible constraints
fcstep = 0
; Frequency of steepest descents steps when doing CG
nstcgsteep = 1000
nbfgscorr = 10
; OUTPUT CONTROL OPTIONS
; Output frequency for coords (x), velocities (v) and forces (f)
nstxout = 0
nstvout = 0
nstfout = 0
; Checkpointing helps you continue after crashes, they are always included now
; Output frequency for energies to log file and energy file
nstlog = 100
nstenergy = 100
; Output frequency and precision for xtc file
nstxout-compressed = 0
compressed-x-precision = 1000
; This selects the subset of atoms for the xtc file. You can
; select multiple groups. By default all atoms will be written.
xtc-grps =
; Selection of energy groups
energygrps =
; NEIGHBORSEARCHING PARAMETERS
; nblist update frequency
nstlist = 10
; ns algorithm (simple or grid)
ns_type = grid
; Periodic boundary conditions: xyz (default), no (vacuum)
; or full (infinite systems only)
pbc = xyz
; nblist cut-off
rlist = 1.2
; OPTIONS FOR ELECTROSTATICS AND VDW
; Method for doing electrostatics
coulombtype = pme
rcoulomb-switch = 0
rcoulomb = 1.2
; Dielectric constant (DC) for cut-off or DC of reaction field
; Method for doing Van der Waals
vdw-type = Cut-off
vdw-modifier = Potential-switch
; cut-off lengths
rvdw-switch = 0.9
rvdw = 1.0
; Apply long range dispersion corrections for Energy and Pressure
DispCorr = AllEnerPres
; Extension of the potential lookup tables beyond the cut-off
; Spacing for the PME/PPPM FFT grid
fourierspacing = 0.10
; FFT grid size, when a value is 0 fourierspacing will be used
fourier_nx = 0
fourier_ny = 0
fourier_nz = 0
; EWALD/PME/PPPM parameters
pme_order = 6
ewald_rtol = 1e-06
ewald_geometry = 3d
epsilon_surface = 0
; OPTIONS FOR WEAK COUPLING ALGORITHMS
; Temperature coupling
Tcoupl = no
; Groups to couple separately
tc-grps = System
; Time constant (ps) and reference temperature (K)
tau_t = 2.0
ref_t = 298.15
; Pressure coupling
Pcoupl = no
Pcoupltype = isotropic
; Time constant (ps), compressibility (1/bar) and reference P (bar)
tau_p = 1
compressibility = 4.5e-5
ref_p = 1.01325
; GENERATE VELOCITIES FOR STARTUP RUN
gen_vel = yes
gen_temp = 298.15
gen_seed = 1993
; OPTIONS FOR BONDS
constraints = hbonds
; Type of constraint algorithm
constraint-algorithm = Lincs
; Do not constrain the start configuration
continuation = no
; Use successive overrelaxation to reduce the number of shake iterations
Shake-SOR = no
; Relative tolerance of shake
shake-tol = 1e-04
; Highest order in the expansion of the constraint coupling matrix
lincs-order = 12
; Number of iterations in the final step of LINCS. 1 is fine for
; normal simulations, but use 2 to conserve energy in NVE runs.
; For energy minimization with constraints it should be 4 to 8.
; Lincs will write a warning to the stderr if in one step a bond
; rotates over more degrees than
lincs-warnangle = 30
; Convert harmonic bonds to morse potentials
morse = no
; ENERGY GROUP EXCLUSIONS
; Pairs of energy groups for which all non-bonded interactions are excluded
energygrp_excl =
; Free energy control stuff
free-energy = yes
init_lambda_state = 0
fep_lambdas = 0.0 0.25 0.5 0.75 1.0 1.00 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
vdw_lambdas = 0.0 0.00 0.0 0.00 0.0 0.05 0.1 0.2 0.3 0.4 0.5 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1.0
;couple-moltype = LIG
couple-lambda0 = none
couple-lambda1 = none
couple-intramol = yes
sc-alpha = 0.5
sc-sigma = 0.3
sc-power = 1.0
sc-r-power = 6
sc-coul = no
nstdhdl = 100
calc-lambda-neighbors = -1
—
Dr. Stefania Evoli
Post-Doctoral Fellow
King Abdullah University of Science and Technology
Catalysis center - Bldg. 3, 4th floor, 4231–WS18
Thuwal, Kingdom of Saudi Arabia
stefania.evoli at kaust.edu.sa
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