Error: fix heat group has no atoms

Hi, Guys,

I always got the error: “fix heat group has no atoms”, by doing NEMD simulation for ThermalConductivity of Argon.

I post my input as following. Would somebody can give me some good suggestions? I double checked the mannual and input, but i didnt find any mistake. I even tried “fix heating all heat 1 0.01 region hot” and "

fix cooling all heat 1 -0.01 region cold". But it still gave me error.

NEMD simulation of Ar thermal conductivity

clear

units lj

log log.Ar05NEMDT0.9

variable T equal 0.9

dimension 3

newton on

boundary p p p

atom_style atomic

neighbor 0.3 bin

neigh_modify check yes

lattice fcc 0.844

region box block 0 4 0 4 0 96 units lattice

create_box 1 box

create_atoms 1 box

region hot block INF INF INF INF 72 72.25 units lattice

group hot region hot

region cold block INF INF INF INF 24.0 24.25 units lattice

group cold region cold

mass 1 1.0

pair_style lj/cut 2.5

pair_coeff 1 1 1.0 1.0 # LJ parameters for Ar-Ar

velocity all create $T 458127641 mom yes rot yes dist gaussian units box

timestep 0.0002

thermo_style custom step temp etotal vol press

thermo_modify lost warn

thermo 1000

fix temp all temp/berendsen $T $T 100

fix NVE all nve

run 500000

unfix temp

unfix NVE

fix nve all nve

compute ke all ke/atom

variable temp atom c_ke/(1.5*1.0)

fix temp_profile all ave/spatial 1 1000000 1000000 z lower 0.25 v_temp file v5temp0.9.profile units lattice

compute hot_temp all temp/region hot

compute cold_temp all temp/region cold

fix heating hot heat 1 0.01 region hot -----> errors coming from

fix cooling cold heat 1 -0.01 region cold

run 2000000

Thanks! Have a good evening!

Yanfei

It is simply because you do not have any atoms in the hot and cold
regions. Adding an additional keyword "region" will not help since
the atom then must be in both the group and the specified geometric
region to have an effect. Please see the doc page.

The mistake is the dynamics, not fix heat. Atoms moved out of the
hot/cold regions due to bad dynamics, hence the error. Please check
your structure, pair_style and pair_coeff settings, and try to
visualize your system.

Ray