Encountering the Error: Invalid Type for Mass Set

LAMMPS LAMMPS Beginners
1

Hello Everyone,

I am trying to simulate the following script:
#Create a simulation box

dimension 3
units metal
boundary p p p
atom_style full

lattice fcc 5
region surface block -20 20 -20 20 -10 0
create_box 1 surface
create_atoms 1 region surface

read_data Waterdrop_atoms.txt add append

mass 1 55.845

pair_style lj/cut 10
pair_coeff 1 1 0.01006418 3.3952

#Perform minimisation
minimize 1e-20 1e-20 10000 10000
timestep 0.01

#Initial Velocity
velocity all create 400 102938 dist gaussian mom yes rot yes

fix 1 all nve

dump dump_1 all custom 100 yt.dump id type x y z ix iy iz vx vy vz
thermo_style custom step time temp pe ke etotal press vol

thermo 100
run 200

undump dump_1
unfix 1

The data file is:
#Coordinates

3800 atoms

4 atom types

-100. 100. xlo xhi
-100. 100. ylo yhi
-50. 50. zlo zhi

Masses

1 18
2 196
3 107
4 23

Atoms

1 1 1 0 1.509267 36.750972 37.461437
2 1 1 0 -42.557439 -5.667561 9.501938
3 1 1 0 -34.853179 -31.671460 14.327726
4 1 1 0 18.444937 -21.530008 24.174740
…

and encountering the error mentioned in the title.
Lammps version: LAMMPS 64-bit 31Aug2021-MPI
Platform: Windows

Can anyone help? Thanks for your time.

2

You create your box with reserved space for only a single atom type and then try to add a data file with settings for 4 atom types. That cannot work. Please re-read the documentation for create_box and read_data.

3

Thanks a lot, Sir. That solved the problem.