[Pw_forum] Shall we calculate some of the parameters by USPP and some other properties by norm conserving PP for same compound?

[Eduardo Menendez]

Dear Sudha,
One expects that all the pseudopotentials lead to the same electronic
structure that an all-electron calculation. Small numerical differences are
expected.
This page is useful https://molmod.ugent.be/deltacodesdft for better
understanding
You should test that the density of states or the bands, are "the same"
computed with both sets of peudopotentials. There will be small numerical
differences. You should also check the lattice parameteres. Variations
smaller than 1% (using the same xc functional) are reasonable. To compute
optical properties with the NC you may use the relaxed structure obtained
either with USPP or with NC. Small numerical differences are also expected
and are acceptable. Care is needed if the differences become  qualitative.
If you use the USPP structure, with NC the same strusctire is stressed, and
the stress and  cause splitting of some levels and some peaks in the
optical properties.
Best regards
Eduardo

--------- Mensaje reenviado ----------
From: Sudha Priyanka <sudhapriyanga24 at gmail.com>
To: PWSCF Forum <pw_forum at pwscf.org>
Cc:
Bcc:
Date: Fri, 12 Jan 2018 04:25:20 -0800
Subject: [Pw_forum] Shall we calculate some of the parameters by USPP and
some other properties by norm conserving PP for same compound?
Dear Experts,
   I did scf and other calculation by using USPP, but in epsilon
calculation (optical properties) I have no option but have to use only norm
conserving PP, Is this correct? Will it make any difference? Shall I
compare the calculated properties and parameters by using these different
pseudopotentials? For example, If I have calculated electronic properties
by USPP and optical properties by norm conserving PP, can I do
interpretation of these properties for the same compound?

With warm regards
Sudha Priyanka G
Assistant Professor,
Lady Doak College,
Madurai, Tamilnadu, India.
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