# harmonic bond style

Dear All users

I know in lammps manual there are this topic:

bond_style harmonic :

E=K(r-r0)^2

where r0 is the equilibrium bond distance. Note that the usual 1/2
factor is included in K.

Dear All users

I know in lammps manual there are this topic:

bond_style harmonic :

E=K(r-r0)^2

where r0 is the equilibrium bond distance. Note that the usual 1/2
factor is included in K.

--------

I want to reproduce a paper, In that paper, I have this term for
harmonic bond style:

E= 1/2k(r-r0)^2 k= 39.0623 ev

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I was a bit confused, I do not understand exactly, Which number should
I use in my input, 39.0623 or (39.0623/2)?

this is the kind of assignment in math for a student in 6th grade (at least
it was for me). i recommend you'll find yourself a 6th grader and let him
explain it to you.

axel.

p.s.: bonus points if you can spot which marx brothers movie this is
referring to.

Dear Axel

You are kidding me while it is necessary for me to understand exactly
this topic,

I want to be sure about my detail numbers in my input script,

showing me your

In fact, I do not understand that topic.

so if you really want to exactly understand what LAMMPS does, why don’t you set up a simple example to see how the K is handled?
a look at the source code should do the trick too…

best,

nikita

Dear Axel

You are kidding me while it is necessary for me to understand exactly
this topic,

no. i am dead serious. you have equation 1:

E=K(r-r0)^2

and you have equation 2:

E= 1/2k(r-r0)^2

if k=39.0623 eV what is the value of K?

since (r-r0)^2 doesn't change you can just call it B.

so now you have:

E=K*B

and

E=1/2*k * B

I want to be sure about my detail numbers in my input script,

there are good questions and there a bad questions. i am trying to point
out to you in as diplomatic a way as i can, that this is a question that
should have you be embarrassed about in eternity (rather than acting like a
spoiled brat).

In fact, I do not understand that topic.

then you should perhaps look for a different profession. you can't do
science without understanding basic calculus. sorry.

axel.

I want to be sure about my detail numbers in my input script,

here are good questions and there a bad questions. i am trying to point out to you in as diplomatic a way as i can, that this is a >question that should have you be embarrassed about in eternity (rather than acting like a spoiled brat).

ok - everyone can calm down - I think the issue here for Ali
is not the math, so much as being unsure what LAMMPS is
really doing. I.e. LAMMPS is a black box and some people
are unsure as to what the black box does.

The suggestion of Nikita is a good one. Try it out for
yourself. Build a system with 2 atoms and 1 bond. Run
it for 0 steps and dump out the forces on each atom for
a value of K that you input. Then change K and see
if the forces changes as you expect. You can compute the
bond formula by hand to see if the forces are what you
expect.

If you don't want to open the box and look at the source code, then the
way to figure out what a black box does, is to use it
and monitor its output as a function of the input.

Steve

Dear Steve and Axel

I read the source code, I have to read that before mailing my post,

Today, I saw one of my teachers in primary school, He was always angry, He was

punishing all of the students in our class for laziness of one student
every day,

His motto was this : " punishment for all and courage for one"

I think it is better for me to start from primary school but My
teacher have to be Axel

because he is really friendly so I can learn very well:)))

I am joking dear Axel:)))))

Dear Steve and Axel

I read the source code, I have to read that before mailing my post,

Today, I saw one of my teachers in primary school, He was always angry, He was

punishing all of the students in our class for laziness of one student
every day,

His motto was this : " punishment for all and encourage just for one"

I think it is better for me to start from primary school but My
teacher have to be Axel

because he is really friendly so I can learn very well:)))

I am joking dear Axel:)))))

Dear Steve and Axel

I read the source code, I have to read that before mailing my post,

so you found out what you wanted to know by yourself?

great. that was the reason for the whole exercise.

and you learned something on top of that. that is a bonus. lets just
i had an overdose of watching groucho marx in the movie "duck soup"
recently. axel.

ps: