input variables
Moderator: rangel

 Posts: 15
 Joined: Fri Jun 21, 2019 12:11 pm
input variables
Hi all
I am new to ABINIT and am learning it. I have a doubt in the usage of variables ngkpt, nkpt and thier consequences and I am asking this in the context of base 3_4 tutorial.
Thanks in advance,
Sai krishna
I am new to ABINIT and am learning it. I have a doubt in the usage of variables ngkpt, nkpt and thier consequences and I am asking this in the context of base 3_4 tutorial.
Thanks in advance,
Sai krishna
Re: input variables
Dear Sai krishna,
nkpt is the total number of kpoints and ngkpt is used in the calculation while to set the number of kpoint in each direction ngkpt is used. Usually ngkpt is used in the input and nkpt is automatically calculated depending on the symmetries of the system and it is better to let the code calculating it.
Best wishes,
Eric
nkpt is the total number of kpoints and ngkpt is used in the calculation while to set the number of kpoint in each direction ngkpt is used. Usually ngkpt is used in the input and nkpt is automatically calculated depending on the symmetries of the system and it is better to let the code calculating it.
Best wishes,
Eric

 Posts: 15
 Joined: Fri Jun 21, 2019 12:11 pm
Re: input variables
Hi Eric
Thank you for the answer but I have doubt in how is k points generated from the ngkpt and how is nkpt calculated?
Thanks in advance
Sai krishna.
Thank you for the answer but I have doubt in how is k points generated from the ngkpt and how is nkpt calculated?
Thanks in advance
Sai krishna.
Re: input variables
Dear Sai krishna,
nkpt is calculated by taking into account the symmetry of the crystal (if with kptopt=1) such that nkpt will be the number of inequivalent kpoints to reduce the size of the calculation.
Best wishes,
Eric
nkpt is calculated by taking into account the symmetry of the crystal (if with kptopt=1) such that nkpt will be the number of inequivalent kpoints to reduce the size of the calculation.
Best wishes,
Eric

 Posts: 15
 Joined: Fri Jun 21, 2019 12:11 pm
Re: input variables
Hey Eric
I have understood your answer and can you tell the role of shiftk?
Thanks in advance
Sai krishna
I have understood your answer and can you tell the role of shiftk?
Thanks in advance
Sai krishna
Re: input variables
Hello,
The variable shiftk is used to shift the kpoint grid by a fixed amount after Abinit determines the list of irreducible kpoints. For most calculations, one can safely set shiftk = 0 0 0 and nshiftk = 0.
See https://docs.abinit.org/variables/basic/#shiftk for additional information and some examples.
Nick
The variable shiftk is used to shift the kpoint grid by a fixed amount after Abinit determines the list of irreducible kpoints. For most calculations, one can safely set shiftk = 0 0 0 and nshiftk = 0.
See https://docs.abinit.org/variables/basic/#shiftk for additional information and some examples.
Nick
Nicholas A. Pike
Research Scientist
Research Scientist

 Posts: 6
 Joined: Fri Nov 29, 2019 5:01 pm
Re: input variables
Yeah, sometimes you want to calculate based on a grid point that isn't zeroed, and like that, you don't have to try to calculate stuff approximatively when compensating for another starting point.