About auto velocity auto correlation function

Dear All

I could get vacf by using compute

is the result of vacf from compute <V(t)V(0)> ?

Then is it possible to get directly <V(t)V(0)> from lammps ?

Best regards.

Please check out the documentation of the compute vacf command — LAMMPS documentation
It answers both your questions.

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Thanks so much.

I will check your link

" Then is it possible to get directly <V(t)V(0)> from lammps ? " is wrong

is it possible to get directly <V(0)V(0)> from lammps ?

(is there any command to get <V(0)V(0)> like vacf command ?)


I disagree with both your statements.

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Sorry for your inconvenience.


how can i get V(0) that is described in the vacf ?

is V(0) velocity of 1st step?

ex) dump all custom 1 vel0.txt id vx vy vz
So is 1st line of vel0.txt V(0)?

Best regards

This is a superfluous question.

You either completely understand the documentation, then there is no question. Or you make a test and can (rather easily for a small enough test system) confirm this with some simple calculus. You cannot expect that somebody will give you a digested version and anticipates all questions. In addition, you should make an effort to formulate your posts more cleanly and consistently. You are not making it easy to understand what you are actually after since you use incomplete and incorrect grammar and contradict yourself (which may be due to a typo, but those can be fixed by re-editing your post(s)).

When reading a documentation you seem to expect that everything your are looking for will be spelled out in great detail right as you need it and as if the author of the documentation had just read your mind. But that is rarely the case, since nobody can anticipate what all the thousands of people that will be looking at the documentation are looking for and how they expect things to be described. Thus you have to take all the bits and pieces that are described and explained and then construct what you need to know from it. Usually, this is rather straightforward and mostly requires logical thinking and a bit of common sense.

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Thank you for your advice.

first I will try it!

Best regards