# shock compression and heat flow simultaniously

Dear all,

I want to study a system may be metallic, polymer, alloy etc where I intend to see what happen if a compression is applied in a surface and simultaneously if we allow heat to flow along the compression direction. This compression may be a small shock. As I have some prior experience to setting up arrangement to generate a shock by using Lammps with wall/piston and velocity command. Here my questions are-

1. would it be logical to use fix_heat to set heat to flow through the entire representative material when I am setting velocity as desired by velocity command to generate a shock. Where fix heat also re scale the velocity to establish a temp gradient along the material.

2. In case of only shock compression I used NVE method to study the system behavior, in this case Can I use “velocity” setting command and Fix_heat simultaneously with nve ? will this simulation be physically meaningful ? (As in many practical cases this type of incident happen)

3. Is their any restriction to use ave/spatial when my simulation domain change with time. To do some spatial average over some small bins I used ave/spatial, but it gives error " cant use ave/spatial when simulation box is changing ". My boundary condition was fs p p and I used wall/reflect.

any exchange of knowledge would be appreciated…

Best Regds,

Cheng Batista
Ph.D Student
IISc Bangalore
India

Steve

Dear all,

I want to study a system may be metallic, polymer, alloy etc where I intend
to see what happen if a compression is applied in a surface and
simultaneously if we allow heat to flow along the compression direction.
This compression may be a small shock. As I have some prior experience to
setting up arrangement to generate a shock by using Lammps with wall/piston
and velocity command. Here my questions are-

I don't know what you mean by "allow heat to flow". How would you stop it?
Heat is just kinetic energy of atoms, it will flow naturally as atoms interact.

1. would it be logical to use fix_heat to set heat to flow through the
entire representative material when I am setting velocity as desired by
velocity command to generate a shock. Where fix heat also re scale the
velocity to establish a temp gradient along the material.

2. In case of only shock compression I used NVE method to study the system
behavior, in this case Can I use "velocity" setting command and Fix_heat
simultaneously with nve ? will this simulation be physically
meaningful ? (As in many practical cases this type of incident happen)

You can use fix heat with fix nve. The velocity command changes velocities
one time, before a run is executed. It has no effect on velocities during
a run.

3. Is their any restriction to use ave/spatial when my simulation domain
change with time. To do some spatial average over some small bins I used
ave/spatial, but it gives error " cant use ave/spatial when simulation box
is changing ". My boundary condition was fs p p and I used wall/reflect.

From the fix ave/spatial doc page:

When the ave keyword is set to running or window then the number of
bins must remain the same during the simulation, so that the
appropriate averaging can be done. This will be the case if the
simulation box size doesn't change or if the units keyword is set to
reduced.

Otherwise the doc page explains how atoms that may be outside the original
set of bins are mapped to a bin.