Spherical vs cartesian basis sets

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Hi,
Il am trying to run a DFT calculation using both one of Pople's basis sets and the LANL2DZ ECP, which are respectively defined with cartesian and spherical-harmonics angular functions. First, I did not specify the "SPHERICAL" keyword in the basis block and the calculation ended successfully but I got the following warning :

        • WARNING Zero Coefficient **** on atom "Au"
angular momentum value: 0  standard basis set name: "lanl2dz ecp"

And the calculation did use 6 d orbitals. Should I ignore this warning? Is the "SPHERICAL" keyword essential when using LANL2DZ? Since the Pople's basis is only used for hydrogen and carbons atom without any d orbital, would it be better to set "SPHERICAL"? Would that affect at all the basis on those atoms?

Thank you,

Chloe

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Hi Cloe,

Yes you can ignore this warning. It mainly provides a sanity check for people that manually input basis sets.

The choice of spherical vs cartesian basis sets is pretty much a personal choice. Generally, the spherical basis set ends up having less linear dependency issues.

Bert


Quote: Jan 6th 4:10 pm
Hi,
Il am trying to run a DFT calculation using both one of Pople's basis sets and the LANL2DZ ECP, which are respectively defined with cartesian and spherical-harmonics angular functions. First, I did not specify the "SPHERICAL" keyword in the basis block and the calculation ended successfully but I got the following warning :

        • WARNING Zero Coefficient **** on atom "Au"
angular momentum value: 0  standard basis set name: "lanl2dz ecp"

And the calculation did use 6 d orbitals. Should I ignore this warning? Is the "SPHERICAL" keyword essential when using LANL2DZ? Since the Pople's basis is only used for hydrogen and carbons atom without any d orbital, would it be better to set "SPHERICAL"? Would that affect at all the basis on those atoms?

Thank you,

Chloe

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The Pople basis sets were defined to use cartesian D functions (but spherical F). This is an artifact of the implementation of integral codes.

The Dunning basis sets were designed to be used with spherical DFGH... functions and to use them with cartesian DFGH... functions is not correct, although the correctness ramifications are less severe since the basis set is just overcomplete. However, the energies will be lower (certainly for variational methods, but probably also for MBPT and CC) than the reference values.


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