# Reg_thermal conductivity of polymers ( all atom model)

​Hi,

I am trying to find thermal conductivity of polymers. I have tried to find thermal conductivity of argon where all the atoms are identical. We can define two regions one is hot and other is cold by adding or removing temperature to particular set of atoms forming a region. Fix thermal conductivity can be used to trace out the conductivity of argon.

But when coming to polymers, in which all atoms are different, I am struggling to define the region with hot and cold temperature. Can anyone has any idea how to find thermal conductivity for polymers (all atom model)?

Is there any boundary condition similar to fix wall/reflect, where we can add heat source at one end and heat sink at the other, so that there will be a temperature gradient from which probably we can find the thermal conductivity?

Also, I have come across one paper where they have mentioned " eg., a region of 2.5A° is defined as heat source". When they have a heat source for 2.5A° it means they have added temperature to all the atoms which ever is that region or it means something else?

Can we use phantom molecules in LAMMPS?

Thank you,

Santhosh.

​Hi,

I am trying to find thermal conductivity of polymers. I have tried to
find thermal conductivity of argon where all the atoms are identical. We
can define two regions one is hot and other is cold by adding or removing
temperature to particular set of atoms forming a region. Fix thermal
conductivity can be used to trace out the conductivity of argon.

But when coming to polymers, in which all atoms are different, I am
struggling to define the region with hot and cold temperature. Can anyone
has any idea how to find thermal conductivity for polymers (all atom model)?

​there are multiple ways with different benefits and difficulties.​

for examples and an overview ​please have a look​ at examples/KAPPA and the
relevant talk slides from here
lammps.sandia.gov/tutorials.html

​for details please have a look at the relevant original literature and
statistical mechanics text books.

axel.​