Correct density of pentane in npt simulation in lammps?

I am trying to get correct density of pentane using trappe force field. I have used 153 molecules with box length 303030. I should get density of 0.673 gm/cc but its comming to be 0.61 gm/cc at 313.15 K and 60 bar. please anyone tell me where can i go wrong?

input file:

# created by fftool

units real
boundary p p p

atom_style full
bond_style harmonic
angle_style harmonic
dihedral_style opls


pair_style  lj/cut 14.0
pair_modify tail yes


read_data data.lmp

pair_coeff    1    1   0.19474     3.750000  # C1 C1
pair_coeff    1    2   0.13340     3.85  # C1 C2
pair_coeff    2    2   0.09141     3.950000  # C2 C2


neighbor 2.0 bin

timestep 1.0

variable TK equal 313.15
variable PBAR equal 59.215

velocity all create ${TK} 12345

fix TPSTAT all npt temp ${TK} ${TK} 100 iso ${PBAR} ${PBAR} 800

thermo 1000
thermo_style custom step cpu etotal temp press lz density

dump TRAJ all custom 10000 dump.lammpstrj id mol type element q xu yu zu
dump_modify TRAJ element C C

run 500000

Is the force field that you are using supposed to provide the exact density?

I am confused by the fact that you dump the per-atom charge. Do your atoms have charges != 0?
If yes, then why do you use pair style lj/cut only?
If no, then why do you output them?