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METAGGA

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METAGGA = TPSS | RTPSS | M06L | MBJ | SCAN | MS0 | MS1 | MS2
Default: METAGGA = none 

Description: selects one of various meta-GGA functionals.


  • METAGGA=TPSS, RTPSS, or M06L
The implementation of the TPSS and RTPSS (revised-TPSS) selfconsistent meta-generalized gradient approximation within the projector-augmented-wave method in VASP is discussed by Sun et al.[1] For details on the M06-L functional read the paper of Zhao and Truhlar.[2]
  • METAGGA=MS0, MS1 and MS2
The MS (where MS stands for "made simple") functionals are presented in detail in references [3] and [4]. These functionals are believed to improve the description of noncovalent interactions over PBE, TPSS and revTPSS but not over M06L. The MS functionals are available from vasp.5.4.1 upwards.
  • METAGGA=MBJ
The modified Becke-Johnson exchange potential in combination with L(S)DA-correlation[5] [6] yields band gaps with an accuracy similar to hybrid functional or GW methods, but computationally less expensive (comparable to standard DFT calculations). The modified Becke-Johnson potential is a local approximation to an atomic exact-exchange potential plus a screening term and is given by:
where ρσ denotes the electron density, τσ the kinetic energy density, and VBR(r) the Becke-Roussel potential:
The Becke-Roussel potential was introduced to mimic the Coulomb potential created by the exchange hole. It is local and completely determined by ρσ, ∇ρσ, ∇2ρσ, and τσ. The function bσ is given by:
and
where α and β are two free parameters, that may be set by means of the CMBJA and CMBJB tags, respectively. The defaults of α=−0.012 (dimensionless) and β=1.023 bohr1/2 were chosen such that for a constant electron density roughly the LDA exchange is recovered. Alternatively one may also set the c parameter directly, by means of the CMBJ-tag.
N.B.I: The mBJ functional is a potential-only functional, i.e., there is no corresponding mBJ exchange-correlation energy, instead Exc is taken from L(S)DA. This means mBJ calculations can never be self-consistent with respect to the total energy, which in turn means we can not compute Hellmann-Feynman forces (i.e., no ionic relaxation etc). These calculations aim solely at a description of the electronic properties, primarily band gaps.
N.B.II: The mBJ calculations converge very slowly in the SCF cycle so the number of maximum electronic steps (NELM) should be set higher than usual.
N.B.III: The mBJ calculations tend to diverge for surface calculations. In the vacuum, where the electron density ρ and kinetic energy density τ are (close to) zero, the functional becomes unstable.


  • METAGGA=SCAN
The SCAN (Strongly constrained and appropriately normed semilocal density functional) [7] is a functional that fulfills all known constraints that the exact density functional must fulfill. There are indications that this functional is superior to most gradient corrected functionals [8]. This functional is only available from vasp.5.4.3 upwards.


Beware: meta-GGA calculations require POTCAR files that include information on the kinetic energy density of the core-electrons. To check whether a particular POTCAR contains this information, type:

grep kinetic POTCAR

This should yield at least the following lines (for each element on the file):

kinetic energy-density
mkinetic energy-density pseudized

and for PAW datasets with partial core corrections:

kinetic energy density (partial)

Convergence issues

If convergence problems are encountered, it is recommended to preconverge the calculations using the PBE functional, to read the PBE WAVECAR file. Furthermore, ALGO = A (conjugate gradient algorithm for orbitals) is often more stable than charge density mixing, in particular, if the system contains vacuum regions.

Related Tags and Sections

CMBJ, CMBJA, CMBJB, LASPH, LMAXTAU, LMIXTAU

Examples that use this tag

References

  1. J. Sun, M. Marsman, G. Csonka, A. Ruzsinszky, P. Hao, Y.-S. Kim, G. Kresse, and J. P. Perdew, Phys. Rev. B 84, 035117 (2011).
  2. Y. Zhao and D. G. Truhlar, J. Chem. Phys. 125, 194101 (2006).
  3. J. Sun, B. Xiao and A. Ruzsinszky, J. Chem. Phys. 137, 051101 (2012).
  4. J. Sun, R. Haunschild, B. Xiao, I. W. Bulik, G. E. Scuseria and J. P. Perdew, J. Chem. Phys. 138, 044113 (2013).
  5. A. D. Becke and E. R. Johnson, J. Chem. Phys. 124, 221101 (2006).
  6. F. Tran and P. Blaha, Phys. Rev. Lett. 102, 226401 (2009).
  7. J. Sun, A. Ruzsinszky, and J. P. Perdew, Phys. Rev. Lett. 115, 036402 (2015).
  8. J. Sun, et al., Nature Chemistry 8, 831–836 (2016).