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<div>Dear Paulatto
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<div>Thanks a lot. I've studied a few about frozen-core approximation in the
papers of Giannozzi about numerical methods in electronic structure. I think
that this approximation is the first step to produce pseudopotential for a
certain atom and then transfer it to particular crystal, but when I
read your answer I became confused,
because you wrote that the pseudopotentials & frozen-core are
different types of approximation.(?)
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<div>Best Regards
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<div>Mehrnaz Anvari
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<div>Iran University Of Science & Technology
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