[Pw_forum] Convergence of Gamma phonon
Subhradip Ghosh
subhra at iitg.ernet.in
Fri Feb 4 07:56:18 CET 2005
Dear All,
I have a question regarding convergence of Gamma phonon for metallic
cases.
I understand that to check the convergence of Gamma phonon frequencies,
one should test convergence with respect to PW cut-off, k-point mesh,
smearing parameter sequentially.
My question is: what is the criteria for acceptable convergence?
Is it only if the difference in gamma phonon frequencies are ~1% witrh
respect
to all of the above parameters?
Is a higher tolerance(say 3%) for gamma phonons permitted?
I am asking this for a specific reason.
I am doing fcc Copper. For the Gamma phonon, increasing the PW cut-off
upto 60 Ryd hasn't given me convergence ~1%. I am using a k-mesh of
12x12x12 without offset.
It seems strange to me that such a high cut-off is required.
Am I going the wrong way? Should I first look for the convergence with
respect to k-mesh?
Subhradip
--
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Dr. Subhradip Ghosh
Assistant Professor
Department of Physics
Indian Institute of Technology, Guwahati
North Guwahati, Assam-781039
India
E-mail: subhra at iitg.ernet.in
Phone: +91 361 2582717(O)
+91 361 2584717(R)
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