LDAUTYPE: Difference between revisions

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Description: {{TAG|LDAUTYPE}} specifies the DFT+U variant that will be used.
Description: {{TAG|LDAUTYPE}} specifies the DFT+U variant that will be used.
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Three variants of the DFT+U approach are available in VASP, that are described in more detail [[DFT+U: formalism|here]] are the following:
The following variants of the [[DFT+U: formalism|DFT+U approach]] are available:


*{{TAG|LDAUTYPE}}=1: The rotationally invariant DFT+U introduced by Liechtenstein ''et al.''{{cite|liechtenstein:prb:95}}
*{{TAG|LDAUTYPE}}=1: The rotationally invariant DFT+U introduced by Liechtenstein ''et al.''{{cite|liechtenstein:prb:95}}


*{{TAG|LDAUTYPE}}=2: The simplified (rotationally invariant) approach to the DFT+U, introduced by Dudarev ''et al.''{{cite|dudarev:prb:98}}
*{{TAG|LDAUTYPE}}=2: The simplified (rotationally invariant) approach to DFT+U, introduced by Dudarev ''et al.''{{cite|dudarev:prb:98}}
:This flavour of DFT+U is of the following form:


*{{TAG|LDAUTYPE}}=4: same as {{TAG|LDAUTYPE}}=1, but without exchange splitting.
*{{TAG|LDAUTYPE}}=3: Linear response ansatz of Cococcioni et al. {{cite|cococcioni:2005}} to compute U. See [[Calculate U for LSDA+U|how to calculate U]].
{{NB|mind|For {{TAG|LDAUTYPE}}{{=}}3, the {{TAG|LDAUU}} and {{TAG|LDAUJ}} tags specify the strength of the spherical potential acting on the spin-up and spin-down manifolds, respectively.|:}}


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*{{TAG|LDAUTYPE}}=4: Same as {{TAG|LDAUTYPE}}=1, but without exchange splitting.
'''Warning''': it is important to be aware of the fact that when using the DFT+U, in general the total energy will depend on the parameters <math>U</math> and <math>J</math> ({{TAG|LDAUU}} and {{TAG|LDAUJ}}, respectively). It is therefore not meaningful to compare the total energies resulting from calculations with different <math>U</math> and/or <math>J</math>, or <math>U-J</math> and in case of Dudarev's approach ({{TAG|LDAUTYPE}}=2).


'''Note on bandstructure calculation''': the {{FILE|CHGCAR}} file contains only information up to angular momentum quantum number <math>l</math>={{TAG|LMAXMIX}} for the [[LDAUTYPE#occmat|on-site PAW occupancy matrices]]. When the {{FILE|CHGCAR}} file is read and kept fixed in the course of the calculations ({{TAG|ICHARG}}=11), the results will be necessarily not identical to a self-consistent run. The deviations are often large for DFT+U calculations. For the calculation of band structures within the DFT+U approach, it is hence strictly required to increase {{TAG|LMAXMIX}} to 4 (<math>d</math> elements) and 6 (<math>f</math> elements).
A method to estimate the parameters for DFT+U is the [[Constrained-random-phase approximation|constrained-random-phase approximation]]. Another method is the linear response ansatz with {{TAG|LDAUTYPE}}=3, mentioned above. On the other hand, in many applications, the DFT+U parameters are used as tuning parameters to fit experimental data.
{{NB|tip|For band-structure calculations, increase {{TAG|LMAXMIX}} to 4 (<math>d</math> elements) or 6 (<math>f</math> elements).}}
This is because the {{FILE|CHGCAR}} file contains only information up to angular momentum quantum number set by {{TAG|LMAXMIX}} for the [[LDAUTYPE#occmat|on-site PAW occupancy matrices]]. When the {{FILE|CHGCAR}} file is read and kept fixed in the course of the calculations ({{TAG|ICHARG}}=11), the results will necessarily not be identical to a self-consistent run. The deviations are often large for DFT+U calculations.
{{NB|warning|The total energy will depend on the parameters <math>U</math> ({{TAG|LDAUU}}) and <math>J</math> ({{TAG|LDAUJ}}). It is, therefore, not meaningful to compare the total energies resulting from calculations with different <math>U</math> and/or <math>J</math>; or <math>U-J</math> in the case of Dudarev's approach ({{TAG|LDAUTYPE}}{{=}}2).}}
 
It is possible to use {{TAG|LDAUTYPE}}=1, 2, and 3 for a non–spin-polarized calculation with {{TAG|ISPIN}}=1.


== Related tags and articles ==
== Related tags and articles ==
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{{TAG|LDAUJ}},
{{TAG|LDAUJ}},
{{TAG|LDAUPRINT}},
{{TAG|LDAUPRINT}},
{{TAG|LMAXMIX}}
{{TAG|LMAXMIX}},
{{TAG|DFT+U: formalism}}


{{sc|LDAUTYPE|Examples|Examples that use this tag}}
{{sc|LDAUTYPE|Examples|Examples that use this tag}}

Latest revision as of 08:53, 9 May 2023

LDAUTYPE = 1 | 2 | 4
Default: LDAUTYPE = 2 

Description: LDAUTYPE specifies the DFT+U variant that will be used.


The following variants of the DFT+U approach are available:

  • LDAUTYPE=1: The rotationally invariant DFT+U introduced by Liechtenstein et al.[1]
  • LDAUTYPE=2: The simplified (rotationally invariant) approach to DFT+U, introduced by Dudarev et al.[2]
Mind: For LDAUTYPE=3, the LDAUU and LDAUJ tags specify the strength of the spherical potential acting on the spin-up and spin-down manifolds, respectively.

A method to estimate the parameters for DFT+U is the constrained-random-phase approximation. Another method is the linear response ansatz with LDAUTYPE=3, mentioned above. On the other hand, in many applications, the DFT+U parameters are used as tuning parameters to fit experimental data.

Tip: For band-structure calculations, increase LMAXMIX to 4 ( elements) or 6 ( elements).

This is because the CHGCAR file contains only information up to angular momentum quantum number set by LMAXMIX for the on-site PAW occupancy matrices. When the CHGCAR file is read and kept fixed in the course of the calculations (ICHARG=11), the results will necessarily not be identical to a self-consistent run. The deviations are often large for DFT+U calculations.

Warning: The total energy will depend on the parameters (LDAUU) and (LDAUJ). It is, therefore, not meaningful to compare the total energies resulting from calculations with different and/or ; or in the case of Dudarev's approach (LDAUTYPE=2).

It is possible to use LDAUTYPE=1, 2, and 3 for a non–spin-polarized calculation with ISPIN=1.

Related tags and articles

LDAU, LDAUL, LDAUU, LDAUJ, LDAUPRINT, LMAXMIX, DFT+U: formalism

Examples that use this tag

References