Clarification on PAO Basis Suffixes, Range of Basis Set Choices, and Recommendations for Magnetic Ex

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Clarification on PAO Basis Suffixes, Range of Basis Set Choices, and Recommendations for Magnetic Ex

Date: 2024/12/26 20:15
Name: shiyc <shiyc814@163.com>: Dear OPENMX Community Members,

I am currently engaged in first-principles calculations using OPENMX and have encountered some uncertainties regarding the selection of pseudopotentials and basis sets. I am hoping to receive some guidance and assistance from the community.

1.Meaning of PAO Basis File Suffixes: I have noticed that the PAO basis files contain suffixes such as 'H', 'S', 'Hp', and 'p'(e.g., Fe4.0H.pao, Fe5.0S.pao, Fe5.0Hp.pao, etc.). Could anyone explain what these suffixes signify? How do they affect the properties of the basis set and the outcomes of the calculations?

2.Range of Basis Set Choices: For an specific element , how can I determine the specific range of orbital types and quantities that are available for selection? Can this be known from the basis set files (*.pao)?

3. Recommendations for calculating Magnetic Exchange Coupling Constants: Are there specific recommendations for choosing basis sets and pseudopotentials for jx calculations, especially for rare-earth elements? What factors should be considered to ensure accuracy in such magnetic properties calculations?

I appreciate any help or guidance you can provide. I look forward to insights from experts and experienced users in the community.

Thank you all!

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Re: Clarification on PAO Basis Suffixes, Range of Basis Set Choices, and Recommendations for Magnetic Ex ( No.1 )

Date: 2025/01/30 21:39
Name: T. Ozaki

Hi,

>1.Meaning of PAO Basis File Suffixes: I have noticed that the PAO basis files contain suffixes
>such as 'H', 'S', 'Hp', and 'p'(e.g., Fe4.0H.pao, Fe5.0S.pao, Fe5.0Hp.pao, etc.).
>Could anyone explain what these suffixes signify?

'H' stands for the hard potential including 3s, 3p, 3d and 4s states as valence,
while 'S' soft one including 3p, 3d and 4s states.
They are explained in
https://www.openmx-square.org/vps_pao2019/Fe/Fe_Soft/index.html
https://www.openmx-square.org/vps_pao2019/Fe/Fe_Hard/index.html

>How do they affect the properties of the basis set and the outcomes of the calculations?
In the above, bench mark calculations are shown. You may notice that the hard one
has a better accuracy.

>2.Range of Basis Set Choices: For an specific element , how can I determine
>the specific range of orbital types and quantities that are available for selection?
>Can this be known from the basis set files (*.pao)?

For the PAO file like Si7.0.pao, '7.0' stands for the range of radial functions in Bohr.

>3. Recommendations for calculating Magnetic Exchange Coupling Constants:
>Are there specific recommendations for choosing basis sets and pseudopotentials
>for jx calculations, especially for rare-earth elements? What factors should be
>considered to ensure accuracy in such magnetic properties calculations?

We recommend to use 'Quick' or 'Standard' as summarized at
https://www.openmx-square.org/openmx_man3.9/node27.html

The use of relatively large basis functions is not recommended, since the dual projector
formula used in the current implemention departs from the localized picture as the size
of basis function are getting larger.

Regards,

TO

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