What do I do when I don't see density in my gromacs energy selection

GROMACS version: 2023.2
GROMACS modification: No

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 

What happens if you try to run gmx density on your system?

You must have mixed up your energy file with one from a non-NPT simultion. With NPT you always get the volume and density and without pressure coupling you don’t.