TAUCAR: Difference between revisions
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The {{FILE|TAUCAR}} file stores | The {{FILE|TAUCAR}} file stores kinetic-energy density | ||
:<math>\tilde \tau_{\sigma\sigma'} = \frac{\hbar^2}{2m} \sum_{n\mathbf{k}} f_{n\mathbf{k}} \mathbf{\nabla} \tilde \psi_{n\mathbf{k}\sigma} \cdot \nabla \tilde \psi_{n\mathbf{k}\sigma'}</math> | |||
in VASP units (eV <math>\AA^{-3}</math>), i.e. the valence contribution of the pseudo expectation value on the plane-wave grid. Here, <math>\mathbf{\nabla} \tilde \psi_{n\mathbf{k}\sigma}</math> is the gradient of the pseudo Kohn-Sham orbitals within the [[PAW method]]. The {{FILE|TAUCAR}} file is written by default for a [[METAGGA|metaGGA]] calculation, but it can also be written for [[XC functionals]] that are independent of <math>\tau</math> by setting {{TAG|LTAU|T}}. The kinetic energy density can also be redirected to {{FILE|vaspwave.h5}} using {{TAG|LH5}}. | |||
To avoid writing <math>\tau</math> for a [[METAGGA|metaGGA]] calculation use {{TAG|LCHARG|F}}. This controls the writing of both the charge density and the kinetic energy density. | |||
The {{FILE|TAUCAR}} file (together with the {{FILE|CHGCAR}} file) can be read to restart a calculation ({{TAG|ICHARG}}). | The {{FILE|TAUCAR}} file (together with the {{FILE|CHGCAR}} file) can be read to restart a calculation ({{TAG|ICHARG}}). | ||
{{NB|tip|We recommend starting from the density files when repeatedly restarting with small changes in the input parameters, e.g., the '''k'''-point mesh ({{FILE|KPOINTS}}).}} | {{NB|tip|We recommend starting from the density files when repeatedly restarting with small changes in the input parameters, e.g., the '''k'''-point mesh ({{FILE|KPOINTS}}).}} | ||
{{NB|mind|Available as of VASP 6.6.}} | {{NB|mind|Available as of VASP 6.6.}} | ||
== Format == | |||
The format is the same as the {{FILE|CHGCAR}} file except for the lack of augmentation occupancies. In other words the {{FILE|TAUCAR}} file consists of the following block: | |||
* Structure in {{FILE|POSCAR}} format | |||
* FFT-grid dimensions {{TAG|NGXF}}, {{TAG|NGYF}}, {{TAG|NGZF}} | |||
* Kinetic energy density | |||
=== Magnetic calculations === | |||
For magnetic calculations, the {{FILE|TAUCAR}} file contains additional data blocks for the magnetic part of <math>\tau</math>. In particular, for spin-polarized calculations ({{TAG|ISPIN}}=2), the first set contains the total kinetic energy density (spin up + spin down) and the second one is the magnetization density (spin up - spin down). For noncollinear calculation ({{TAG|LNONCOLLINEAR}}=T), it contains the total charge density and the magnetic part <math>\tau_m</math> in the spinor basis set by {{TAG|SAXIS}}. | |||
== Related tags and articles == | == Related tags and articles == | ||
Latest revision as of 12:58, 11 March 2026
The TAUCAR file stores kinetic-energy density
- [math]\displaystyle{ \tilde \tau_{\sigma\sigma'} = \frac{\hbar^2}{2m} \sum_{n\mathbf{k}} f_{n\mathbf{k}} \mathbf{\nabla} \tilde \psi_{n\mathbf{k}\sigma} \cdot \nabla \tilde \psi_{n\mathbf{k}\sigma'} }[/math]
in VASP units (eV [math]\displaystyle{ \AA^{-3} }[/math]), i.e. the valence contribution of the pseudo expectation value on the plane-wave grid. Here, [math]\displaystyle{ \mathbf{\nabla} \tilde \psi_{n\mathbf{k}\sigma} }[/math] is the gradient of the pseudo Kohn-Sham orbitals within the PAW method. The TAUCAR file is written by default for a metaGGA calculation, but it can also be written for XC functionals that are independent of [math]\displaystyle{ \tau }[/math] by setting LTAU = T. The kinetic energy density can also be redirected to vaspwave.h5 using LH5.
To avoid writing [math]\displaystyle{ \tau }[/math] for a metaGGA calculation use LCHARG = F. This controls the writing of both the charge density and the kinetic energy density.
The TAUCAR file (together with the CHGCAR file) can be read to restart a calculation (ICHARG).
| Tip: We recommend starting from the density files when repeatedly restarting with small changes in the input parameters, e.g., the k-point mesh (KPOINTS). |
| Mind: Available as of VASP 6.6. |
Format
The format is the same as the CHGCAR file except for the lack of augmentation occupancies. In other words the TAUCAR file consists of the following block:
Magnetic calculations
For magnetic calculations, the TAUCAR file contains additional data blocks for the magnetic part of [math]\displaystyle{ \tau }[/math]. In particular, for spin-polarized calculations (ISPIN=2), the first set contains the total kinetic energy density (spin up + spin down) and the second one is the magnetization density (spin up - spin down). For noncollinear calculation (LNONCOLLINEAR=T), it contains the total charge density and the magnetic part [math]\displaystyle{ \tau_m }[/math] in the spinor basis set by SAXIS.