[gmx-users] System reaches ~124K after simulated annealing upto 300K

[Justin Lemkul]

On 6/16/17 10:38 AM, Apramita Chand wrote:
> Dear All,
> I have used the following nvt.mdp file to gradually warm my system upto
> 300K but just reach upto 124K. I have used variety of options in the
> simulated annealing like taking less no. of time intervals but in vain
> Then, I have to perform manually the gradual heating process which takes me
> to 300K
> Why doesn't this work?
> 

Anything that goes that haywire is simply unstable.  De-complicate your life and 
try to do a normal (non-annealing) MD and see if it works.  If not, then 
diagnose further.

http://www.gromacs.org/Documentation/Terminology/Blowing_Up#Diagnosing_an_Unstable_System

-Justin

> Yours sincerely,
> Apramita
> 
> 
> 
>   VARIOUS PREPROCESSING OPTIONS
> define                   = -DPOSRES
> ; RUN CONTROL PARAMETERS
> integrator               = md
> dt                       = 0.002 ; time step (in ps)
> nsteps                   = 50000 ; number of steps
> ; OUTPUT CONTROL OPTIONS
> nstxout                 = 500   ; save coordinates every ps
> nstvout                 = 500   ; save velocities every ps
> nstenergy               = 500   ; save energies every ps
> nstlog                  = 500   ; update log file every ps
> energygrps              = Protein SOL
> ; NEIGHBORSEARCHING PARAMETERS
> nstlist                  = 5
> ns_type                  = grid
> pbc                      = xyz
> rlist                    = 0.9
> ; OPTIONS FOR ELECTROSTATICS AND VDW
> coulombtype              = PME  ; Particle Mesh Ewald for long-range
> electrostatics
> pme_order                = 4    ; cubic interpolation
> fourierspacing           = 0.16 ; grid spacing for FFT
> rcoulomb                 = 0.9
> vdw-type                 = Cut-off
> rvdw                     = 1.4
> ; Temperature coupling
> 5
> tcoupl                   = v-rescale            ; Couple temperature to
> external heat bath according to velocity re-scale method
> tc-grps                  =  Protein  SOL ; Use separate heat baths for
> Protein and Non-Protein groups
> tau_t                    = 0.1        0.1        ; Coupling time constant,
> controlling strength of coupling
> ref_t                    = 300        300    ; Temperature of heat bath
> ; Dispersion correction
> DispCorr                 = EnerPres ; account for vdw cut-off
> ; Pressure coupling is off
> pcoupl                  = no                    ; no pressure coupling in
> NVT
> ; GENERATE VELOCITIES FOR STARTUP RUN
> gen_vel                  = yes    ; Assign velocities to particles by
> taking
> them randomly from a Maxwell distribution
> Different numbers give different sets of velocities
> gen_temp                 = 300    ; Temperature to generate corresponding
> Maxwell distribution
> gen_seed                 = -1     ; Seed for (semi) random number
> generation.
> ; OPTIONS FOR BONDS
> constraints              = all-bonds ; All bonds will be treated as
> constraints (fixed length)
> continuation             = no           ; first dynamics run
> constraint_algorithm     = lincs        ; holonomic constraints
> lincs_iter               = 1            ; accuracy of LINCS
> lincs_order              = 4            ; also related to accuracy
> ; Simulated Annealing
> annealing= single single
> annealing_npoints= 4 4
> annealing_time= 0 50 75 100 0 50 75 100
> annealing_temp= 0 100 200 300 0 100 200 300
> 

-- 
==================================================

Justin A. Lemkul, Ph.D.
Ruth L. Kirschstein NRSA Postdoctoral Fellow

Department of Pharmaceutical Sciences
School of Pharmacy
Health Sciences Facility II, Room 629
University of Maryland, Baltimore
20 Penn St.
Baltimore, MD 21201

jalemkul at outerbanks.umaryland.edu | (410) 706-7441
http://mackerell.umaryland.edu/~jalemkul

==================================================