[lammps-users] why problem with fix msd??

i am reading the manual about fix msd and compute msd. compute command defines the computation and the fix msd calculates it. So i write in my input file:
(b) A part of my input file is :

dimension 3
boundary p p p
units real
neighbor 0.3 bin
neigh_modify delay 4 every 1
atom_style atomic
pair_style lj/cut 10
pair_modify mix arithmetic

read_restart CO2data.min.restart

pair_coeff 1 1 0.468781652037 3.454

compute 1 all msd
fix 1 all msd 100 diff.out
fix 2 all npt temp 300 300 100.0 iso 0.98 0.98 100

thermo 300
thermo_style multi
timestep 0.5
run 200

write_restart co2.equil.restart

thermo 500
log produc.log
thermo_style custom etotal ke temp pe ebond eangle ecoul press vol
thermo_modify line multi

timestep 1.0
run 2000

There is no longer a fix msd command - it is now compute msd.
So you are using doc pages that are inconsistent with the version
of the src code that you have.