[lammps-users] ERROR: Fix ave/time compute does not calculate a scalar

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1

Hi all,
I am simulating a liquid system.
I am trying to calculate the RDF of particular atom pairs. I followed what the manual says and set up calculation for RDF.
But I am getting this error:

ERROR: Fix ave/time compute does not calculate a scalar

If I change the mode to vector it says the opposite ( Fix ave/time compute does not calculate a vector).

I get similar remarks when I try to compute center of mass (compute ID com and output as c_ID in thermo style output.)

Can anyone suggest me what could be wrong ?

I have attached my input file.
Thanks for any suggestions

Mousumi

INPUT FILE
clear
units real

#Defining the different potential types
pair_style lj/cut/coul/cut 15 15
#kspace_style pppm 0.0001
atom_style full
angle_style harmonic
bond_style harmonic
dihedral_style harmonic
improper_style cvff

#Data Reading and neighbouring information
neighbor 2.0 bin
neigh_modify delay 0 every 1 check yes
#neigh_modify every 2 delay 4 check yes page 100000000

read_restart restart_IL.298
pair_modify shift yes mix arithmetic

#Setting MD parameters
timestep 1.0

fix 3 all npt temp 298 298 100.0 iso 1.0 1.0 1000.0 couple xyz
compute myRDF all rdf 50 8 8 4 4 8 4
fix 4 all ave/time 100 1 100 c_myRDF file tmp.rdf mode scalar

dump 1 all custom 100 trj_rdf.298 type q xu yu zu vx vy vz
thermo_style custom step etotal pe vol
thermo 100

run 250
write_restart restart_rdf.298
unfix 3
unfix 4
undump 1

2

Works for me if I try vector mode. I couldn’t use your input script since I don’t have your restart file, but I tried this input script, and it worked fine:

variable x index 1

variable y index 1

variable z index 1

variable xx equal 20*$x

variable yy equal 20*$y

variable zz equal 20*$z

units lj

atom_style atomic

lattice fcc 0.8442

region box block 0 {xx} 0 {yy} 0 ${zz}

create_box 1 box

create_atoms 1 box

mass 1 1.0

velocity all create 1.44 87287 loop geom

pair_style lj/cut 2.5

pair_coeff 1 1 1.0 1.0 2.5

neighbor 0.3 bin

neigh_modify delay 0 every 20 check no

fix 1 all nve

compute myRDF all rdf 50 1 1 1 1 1 1

fix 10 all ave/time 100 1 100 c_myRDF file tmp.rdf mode vector

run 10

Paul