[CP2K:10502] Something confusing in the calculation of bilayer graphene

[hut... at chem.uzh.ch]

Hi

this is still a rather untested option in CP2K. It might well
be that for non-cubic cells there are still problems with the
definition of k-point paths. This is especially true for older
versions (pre 5.1).
You can try to compare to the results if you use the special
points in the SCF settings.

regards

Juerg Hutter
--------------------------------------------------------------
Juerg Hutter                         Phone : ++41 44 635 4491
Institut für Chemie C                FAX   : ++41 44 635 6838
Universität Zürich                   E-mail: hut... at chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland
---------------------------------------------------------------

-----cp... at googlegroups.com wrote: -----
To: "cp2k" <cp... at googlegroups.com>
From: "Tianshu Jiang in Beijing" 
Sent by: cp... at googlegroups.com
Date: 07/11/2018 08:53AM
Subject: [CP2K:10502] Something confusing in the calculation of bilayer graphene

 Hi everyone, 
 I have been trying to calculate the band structure of bilayer graphene using CP2k 4.1. The input file follow the tutorial band structure of graphene , and is listed in the following 

&GLOBAL
  PROJECT twoLayerGraphBS_z18
  RUN_TYPE ENERGY
  PRINT_LEVEL MEDIUM
&END GLOBAL

&FORCE_EVAL
  METHOD Quickstep
  &DFT
    BASIS_SET_FILE_NAME BASIS_MOLOPT
    POTENTIAL_FILE_NAME POTENTIAL

    &POISSON
      PERIODIC XYZ 
    &END POISSON
    &QS 
      EXTRAPOLATION USE_GUESS
    &END QS
    &SCF
      SCF_GUESS ATOMIC
      EPS_SCF 1.0E-6
      MAX_SCF 300 

      ADDED_MOS 2
      &SMEAR ON
        METHOD FERMI_DIRAC
        ELECTRONIC_TEMPERATURE [K] 300 
      &END SMEAR
      &DIAGONALIZATION
        ALGORITHM STANDARD
        EPS_ADAPT 0.01
      &END DIAGONALIZATION
      &MIXING
        METHOD BROYDEN_MIXING
        ALPHA 0.2
        BETA 1.5
        NBROYDEN 8
      &END MIXING
    &END SCF

    &XC
      &XC_FUNCTIONAL PBE
      &END XC_FUNCTIONAL
    &END XC
    &KPOINTS
      SCHEME MONKHORST-PACK 3 3 1
      SYMMETRY OFF
      WAVEFUNCTIONS REAL
      FULL_GRID .TRUE.
      PARALLEL_GROUP_SIZE 0
      &BAND_STRUCTURE
        ADDED_MOS 6
        FILE_NAME graph_z18.bs
        &KPOINT_SET
          UNITS CART_BOHR
          SPECIAL_POINT 0.0 0.0 0.0
          SPECIAL_POINT 1./2. 0.0 0.0
          SPECIAL_POINT 2./3. 1./3. 0.0
          SPECIAL_POINT 0.0 0.0 0.0
          NPOINTS 80  
        &END
      &END BAND_STRUCTURE
    &END KPOINTS
    &PRINT
        &E_DENSITY_CUBE ON
            STRIDE 1 1 1
        &END E_DENSITY_CUBE
    &END PRINT
  &END DFT
  &SUBSYS
    &CELL
      ABC [angstrom] 2.4612 2.4612 21.0
      ALPHA_BETA_GAMMA 90. 90. 60.
      SYMMETRY HEXAGONAL
      PERIODIC XYZ
      MULTIPLE_UNIT_CELL 1 1 1
    &END CELL
    &TOPOLOGY
      MULTIPLE_UNIT_CELL 1 1 1
    &END TOPOLOGY
    &COORD
      SCALED
      C 1./3. 1./3. 0.
      C 2./3. 2./3. 0.
      C 2./3. 2./3. 1./6.
      C 3./3. 3./3. 1./6.
    &END
    &KIND C
      ELEMENT C
      BASIS_SET TZVP-MOLOPT-GTH
      POTENTIAL GTH-PBE-q4
    &END KIND
  &END SUBSYS

&END FORCE_EVAL




And the band structure I plotted is as follows
The k-point path I choose is : \gamma->M->K->\gamma. There should not exist band gap near the point K and the profile of the line near point K should be parabola. 
Does anyone know where is the problem in my calculation setting ?

Thanks for any kind response !

  
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