fix heat group has no atoms?

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1

Hi, guys,

I am trying to get temp gradient by using “fix heat” command. But it always tell me error: fix heat group has no atoms. I checked that there are still some atoms in hot region. Why it still tell me the error. I checked the syntax and didnt find it wrong.

Part of The input is :

…

lattice fcc 0.844

region box block -20 20 -4 4 -4 4 units lattice

create_box 1 box

create_atoms 1 box

region hot block -1 1 INF INF INF INF units lattice

region cold1 block -20 -19 INF INF INF INF units lattice

region cold2 block 19 20 INF INF INF INF units lattice

group hotregion region hot

group cold1region region cold1

group cold2region region cold2

…

fix nvt

run 500000

unfix nvt

…

fix npt

run 500000

unfix npt

…

fix NVE all nve

fix heating hotregion heat 1 5 region hot

fix cooling1 cold1region heat 1 -5 region cold1

fix cooling2 cold2region heat 1 -5 region cold2

run 2000001

…

2

It is hard to be sure what exactly the problem is without seeing at least the log file and full input, however the first thing that occurs to me is that you appear to be removing heat from the system which in general terms within the NVE ensemble would cause the system to solidify within the “cold” region thus removing particles from the “hot” region.

All the best, Jeff.

3

Hi, guys,

   I am trying to get temp gradient by using "fix heat" command. But it
always tell me error: fix heat group has no atoms. I checked that there
are still some atoms in hot region. Why it still tell me the error. I

there may be atoms, but are those in the group hotatoms?

there is a conceptual flaw in your setup. groups are static.
you are limiting the atoms that the heat fixes are applied
to needlessly twice. so the error message seems quite possible.

axel.