TAUCAR
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.