08 February 2024 0 7K Report

I tried to proceed with NPT as usual in protein MD simulation in water and get the density for the whole system.

However, I don't see any "density" items in my "gmx energy" selection.

The same symptoms appear when I transfer a project file to my desktop because I suspect an abnormality in the installed equipment.

I can be sure that I did not confuse NVT result file with NPT result file.

How can I solve this problem?

I attach the output of the terminal and the contents of the mdp file used for the NPT.

---

gmx energy -f npt.edr -o density-after-npt.xvg

:-) GROMACS - gmx energy, 2023.2 (-:

Executable: /usr/local/gromacs/bin/gmx

Data prefix: /usr/local/gromacs

Working dir: /home/user1/gmx-workdata/TEAD-YAP-80mM

Command line:

gmx energy -f npt.edr -o density-after-npt.xvg

Opened npt.edr as single precision energy file

Select the terms you want from the following list by

selecting either (part of) the name or the number or a combination.

End your selection with an empty line or a zero.

-------------------------------------------------------------------

1 Bond 2 U-B 3 Proper-Dih. 4 Improper-Dih.

5 CMAP-Dih. 6 LJ-14 7 Coulomb-14 8 LJ-(SR)

9 Disper.-corr. 10 Coulomb-(SR) 11 Coul.-recip. 12 Position-Rest.

13 Potential 14 Kinetic-En. 15 Total-Energy 16 Conserved-En.

17 Temperature 18 Pres.-DC 19 Pressure 20 Constr.-rmsd

21 Vir-XX 22 Vir-XY 23 Vir-XZ 24 Vir-YX

25 Vir-YY 26 Vir-YZ 27 Vir-ZX 28 Vir-ZY

29 Vir-ZZ 30 Pres-XX 31 Pres-XY 32 Pres-XZ

33 Pres-YX 34 Pres-YY 35 Pres-YZ 36 Pres-ZX

37 Pres-ZY 38 Pres-ZZ 39 #Surf*SurfTen 40 T-Protein

41 T-non-Protein 42 Lamb-Protein

43 Lamb-non-Protein

---

title = OPLS Lysozyme NPT equilibration

define = -DPOSRES ; position restrain the protein

; Run parameters

integrator = md ; leap-frog integrator

nsteps = 2500000 ; 2 * 2500000 = 5000 ps = 5 ns

dt = 0.002 ; 2 fs

; Output control

nstxout = 500 ; save coordinates every 1.0 ps

nstvout = 500 ; save velocities every 1.0 ps

nstenergy = 500 ; save energies every 1.0 ps

nstlog = 500 ; update log file every 1.0 ps

; Bond parameters

continuation = yes ; Restarting after NVT

constraint_algorithm = lincs ; holonomic constraints

constraints = h-bonds ; bonds involving H are constrained

lincs_iter = 1 ; accuracy of LINCS

lincs_order = 4 ; also related to accuracy

; Nonbonded settings

cutoff-scheme = Verlet ; Buffered neighbor searching

ns_type = grid ; search neighboring grid cells

nstlist = 10 ; 20 fs, largely irrelevant with Verlet scheme

rcoulomb = 1.0 ; short-range electrostatic cutoff (in nm)

rvdw = 1.0 ; short-range van der Waals cutoff (in nm)

DispCorr = EnerPres ; account for cut-off vdW scheme

; Electrostatics

coulombtype = PME ; Particle Mesh Ewald for long-range electrostatics

pme_order = 4 ; cubic interpolation

fourierspacing = 0.16 ; grid spacing for FFT

; Temperature coupling is on

tcoupl = V-rescale ; modified Berendsen thermostat

tc-grps = Protein Non-Protein ; two coupling groups - more accurate

tau_t = 0.1 0.1 ; time constant, in ps

ref_t = 310.15 310.15 ; reference temperature, one for each group, in K = 310.15k = 37C

; Pressure coupling is on

pcoupl = Parrinello-Rahman ; Pressure coupling on in NPT

pcoupltype = isotropic ; uniform scaling of box vectors

tau_p = 2.0 ; time constant, in ps

ref_p = 1.0 ; reference pressure, in bar = 1bar

compressibility = 4.5e-5 ; isothermal compressibility of water, bar^-1

refcoord_scaling = com

; Periodic boundary conditions

pbc = xyz ; 3-D PBC

; Velocity generation

gen_vel = no ; Velocity generation is off

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