# linear rod collapse....

Hello,

I am try to simulate a system containing a linear rod (bond angle = 0).
Even if I use very high bonding/angle energy, the structure collapses or bond angle goes to over 20 degrees.
e.g.,
bond_style harmonic
bond_coeff 1 300.0 0.0
angle_style harmonic
angle_coeff 1 300.0 0.0

Could anyone help me ?
How can I maintain the linear structure of rod?

Thank you.

Isn't a linear rod an angle of 180?

Also, you can do this w/out an angle potential
if you put a psuedo-bond between the 1-3 atoms
with an equil distance of 2*bondlength.

Steve

Thank you.

But it still happens when I try with either angle of 180 or pseudo-bond.

Thank you.
But it still happens when I try with either angle of 180 or pseudo-bond.

you input quote was listing a bond length of 0.
how shall that work at all???

axel.

That was an example.
Actual values I used are:

bond_style harmonic
bond_coeff 1 300.0 1.0
angle_style harmonic
angle_coeff 1 300.0 180.0

When I tried with pseudo bond (style #2),
bond_style harmonic
bond_coeff 1 300.0 1.0
bond_style harmonic
bond_coeff 2 300.0 2.0

Thank you.

That was an example.

if you post a stupid example, you get a stupid answer.

Actual values I used are:

...and they are all useless without being able
to _reproduce_ what you are seeing.

if something doesn't work there are three possible explanations:
- there is something wrong with your input
- it cannot work, because your expectations or your model are wrong
- there is something wrong with lammps

without having the necessary context it is impossible to
know what is causing you problems unless you are a psychic.

axel.