LLRAUG: Difference between revisions

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{{TAGDEF|LLRAUG|.TRUE. {{!}} .FALSE. | .FALSE.}}
{{TAGDEF|LLRAUG|.TRUE. {{!}} .FALSE. | .FALSE.}}


Description: The {{TAG|LLRAUG}} computes the two-center contributions to the chemical shift tensor.
Description: {{TAG|LLRAUG}} calculates the two-center contributions to the chemical shift tensor.
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{{TAG|LLRAUG}} restores the small ''B''-component of the wave function inside
{{TAG|LLRAUG}} switches on two-center contributions to the NMR chemical shift tensor.
the PAW spheres in the linear-response calculation of the NMR chemical shift
These are contributions due to the augmentation
tensor. The POTCARs used in VASP are scalar-relativistic and the
currents in other PAW spheres than the sphere with the atom for which the shift tensor is calculated.
AE-partial waves are solutions of the scalar-relativistic Kohn-Sham
Typically these contributions are safely neglected.
equation for the spherical atom. These have large (''A'') and small (''B'') components.
It makes sense to include them for accurate calculations with hard potentials (<tt>*_h</tt>)
The latter are not retained on the POTCAR, but approximately restored when {{TAG|LLRAUG}}=.TRUE.<ref name="dewijs:jcp:17"/>
on systems containing also (non-hydrogen) atoms from the top rows of the periodic
This is done only in the one-center valence contributions to the chemical shift.
table (B, C, N, O, F), typically with short bonds, e.g. C<sub>2</sub>H<sub>2</sub>, where
Core contributions to the chemical shift always contain contributions from both the ''A'' and ''B'' components.
effects up to a few ppm are possible. Effects are most significant for the H shift. For such systems using standard potentials
typically introduces larger inaccuracies. The two-center contributions are calculated using
a multipole expansion of the current density that is represented on the plane wave grid.<ref name="dewijs:jcp:17"/>
The relevance of {{TAG|LLRAUG}} to achieve basis-set completeness for shieldings is discussed in
Ref.<ref name="dewijs:jcp:18"/> that compares to basis-set converged quantum chemical calculations.<ref name="jenssen:jcp:nmr"/>


== Related Tags and Sections ==
== Related tags and articles ==
{{TAG|LCHIMAG}}
{{TAG|LCHIMAG}}


== References ==
== References ==
<references>
<references>
<ref name="dewijs:jcp:17">[http://aip.scitation.org/doi/10.1063/1.4975122 G. A. de Wijs, R. Laskowski, P. Blaha, R. W. A. Havenith, G. Kresse, M. Marsman, J. Chem. Phys. 146, 064115 (2017).]</ref>
<ref name="dewijs:jcp:17">As in Sec. III.A.3 of [http://aip.scitation.org/doi/10.1063/1.4810799 F. Vasconcelos, G.A. de Wijs, R. W. A. Havenith, M. Marsman, G. Kresse, J. Chem. Phys. 139, 014109 (2013).]</ref>
<ref name="dewijs:jcp:18">[http://aip.scitation.org/doi/10.1063/5.0069637 G.A. de Wijs, G. Kresse, R. W. A. Havenith, M. Marsman, J. Chem. Phys. 155, 234101 (2021).]</ref>
<ref name="jenssen:jcp:nmr">[https://doi.org/10.1039/C6CP01294A S.R. Jensen, T. Flå, D. Jonsson, R.S. Monstad, K. Ruud, L. Frediani, Phys. Chem. Chem. Phys. 18, 21145 (2016).]</ref>
</references>
</references>
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[[The_VASP_Manual|Contents]]


[[Category:INCAR]]
[[Category:INCAR tag]][[Category:NMR]][[Category:Chemical shifts]]

Latest revision as of 14:29, 28 April 2022

LLRAUG = .TRUE. | .FALSE.
Default: LLRAUG = .FALSE. 

Description: LLRAUG calculates the two-center contributions to the chemical shift tensor.


LLRAUG switches on two-center contributions to the NMR chemical shift tensor. These are contributions due to the augmentation currents in other PAW spheres than the sphere with the atom for which the shift tensor is calculated. Typically these contributions are safely neglected. It makes sense to include them for accurate calculations with hard potentials (*_h) on systems containing also (non-hydrogen) atoms from the top rows of the periodic table (B, C, N, O, F), typically with short bonds, e.g. C2H2, where effects up to a few ppm are possible. Effects are most significant for the H shift. For such systems using standard potentials typically introduces larger inaccuracies. The two-center contributions are calculated using a multipole expansion of the current density that is represented on the plane wave grid.[1] The relevance of LLRAUG to achieve basis-set completeness for shieldings is discussed in Ref.[2] that compares to basis-set converged quantum chemical calculations.[3]

Related tags and articles

LCHIMAG

References