How to determine whether delta_approx=.true. needs to be set?

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sevenel
Posts: 9
Joined: Mon Jul 19, 2021 8:12 am
Affiliation: postdcotor

How to determine whether delta_approx=.true. needs to be set?

Post by sevenel »

Dear all,
When calculating phonon linewidth, how to determine whether delta_approx=.true. needs to be set?
When I repeated the example 'q-e-qe-6.7.0/EPW/examples/diamond/epw/' with or notwith the parameter delta_approx=.true. ,
the linewith of phonon are very difference.
best wishes,
zhenqing
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hlee
Posts: 415
Joined: Thu Aug 03, 2017 12:24 pm
Affiliation: The University of Texas at Austin

Re: How to determine whether delta_approx=.true. needs to be set?

Post by hlee »

Dear zhenqing:

When delta_approx is set to .true. , the “double-delta function” approximation is used; the phonon frequencies are neglected in calculating the imaginary part of the phonon self-energy.
So it is more accurate to set delta_approx to .false. (this is a default value).

Sincerely,

H. Lee

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