[Pw_forum] help with /examples/example03

[Amin Torabi]

Hi forum users!

I am a novice in using this package and would appreciate if someone could
help me understand the instruction in /examples/example03

1 I understand that the task of this example is to find the minimum
geometry. but how does it decide to to put the molecule in a box of side 12
bohr? where does 12 come from? Do we have to assign ibrav to zero whenever
we want to optimize the geometry of an electronic system?

2 How do you decide to set ecutwfc to 24? /Doc/INPUT_PW.txt just says that
it is a cutoff energy for wavefunctions. I have no clue how much it should
be

3 How do you set the x-component of the atomic position of carbon to be at
2.256 and all the other one to be zero?

If you can guide me to a file or a link which explains these kind of
questions, it would be great

Thanks
Amin
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