Interpolation Calculation

These variables control the interpolation calculations.

  • Type: STRING
  • Default: ph_save
  • Description: Directory path containing the phonon save data to be read.
  • Type: STRING
  • Default: ph_save_interpolation
  • Description: Directory path where the interpolation results will be written.
  • Type: LOGICAL
  • Default: True
  • Description: If True, the code interpolates the deformation potential (\(\delta V_{scf}\)).
  • Type: LOGICAL
  • Default: False
  • Description: If True, no symmetries are used; i.e., dynamical matrices and dvscf are printed on the full Brillouin zone.
  • Type: STRING
  • Default: no
  • Description: Specifies the type of Acoustic Sum Rule to apply for force constant matrix.
    • no: No acoustic sum rule applied.
    • simple: Simple acoustic sum rule (corrects only the diagonal matrix elements).
    • crystal: Translational acoustic sum rule imposed via orthogonal projection.
    • all: Translational and rotational acoustic sum rules imposed via orthogonal projection.
    • all_huang: (recommended) Translational and rotational sum rules, plus Huang invariances, imposed via orthogonal projection.
  • Type: STRING
  • Default: no
  • Description: Specifies the type of Acoustic Sum Rule to apply for Born charges.
    • no: No acoustic sum rule applied.
    • simple: Simple acoustic sum rule (corrects only the diagonal matrix elements).
    • crystal: Acoustic sum rule imposed via orthogonal projection.
  • Type: LOGICAL
  • Default: False

  • Description: If True, applies non-analytic (LO-TO) splitting corrections to the dynamical matrices at \(\Gamma\) point.

    It should be noted that this flag does not completely switch off LO-TO treatment. It is only intended for switch on/off LO/TO treatment at the Gamma point. If you wish to completely disable LO-TO splitting, please remove or rename the tensors.xml file in the ph_save directory.

    If qlist_file is provided instead of nq1, nq2, and nq3, then loto and loto_dir variables are ignored. See qlist_file for details.

  • Type: REAL (Array of 3)
  • Default: 0.0 0.0 0.0

  • Description: A vector (in cartesian units) specifying the direction approaching the \(\Gamma\) point (\(q \to 0\)) for LO-TO splitting. Internally, the code normalizes the vector, so the user does not need to provide a normalized vector.

    If loto = false, this flag is ignored.

    If the magnitude of the vector is smaller than \(10^{-5}\), it is ignored and treated as loto = false.

    • Format: Three space-separated floats.
    • Example: loto_dir = 1.0 0.0 0.0 (along x-axis)

    If qlist_file is provided instead of nq1, nq2, and nq3, then loto and loto_dir variables are ignored. See qlist_file for details.

  • Type: INTEGER
  • Default: 1
  • Description: Dimensions of the fine q-point grid used for interpolation. Number of q points along reciprocal lattice vector \(b_1\).
  • Type: INTEGER
  • Default: 1
  • Description: Dimensions of the fine q-point grid used for interpolation. Number of q points along reciprocal lattice vector \(b_2\).
  • Type: INTEGER
  • Default: 1
  • Description: Dimensions of the fine q-point grid used for interpolation. Number of q points along reciprocal lattice vector \(b_3\).
  • Type: LOGICAL
  • Default: False
  • Description: If True, the code will dump the change in the local part of the bare potential to disk. Note: in case write_dVbare = True and interpolate_dvscf = False, dyn* files are not written.
  • Type: REAL
  • Default: 1.0
  • Description: Ewald parameter used for screened long-range interactions (dipoles, quadrupoles, phonon dynamical matrices).
    • Must be a positive value.
  • Type: REAL
  • Default: 1.0
  • Description: Ewald summation parameter used specifically for the interpolation of dynamical matrices.
    • Must be a positive value.
  • Type: STRING
  • Default: ""
    • If a non-zero length string is provided, the code interpolates over this list instead of the grid defined by nq1, nq2, nq3.
    • Format: 
      Number of qpoints given in the list
Q1x Q1y Q1z
Q2x Q2y Q2z
# Use # to comment. It will be skiped when reading

    Description: Filename containing a specific list of q-points provided in reduced units to interpolate.

    Note on LO-TO splitting

    When qlist_file is provided, the loto and loto_dir variables are ignored. To obtain LO–TO splitting, include a small direction vector at the \(\Gamma\) point. Instead of sampling exactly at \(\Gamma\), use a displaced point \(\vec{q} = \Gamma + \vec{\epsilon}\), where \(\lvert \vec{\epsilon} \rvert\) is small and defines the direction of approach. When \(\vec{\epsilon}\) vector is converted to caresian units, its magnitude should be small; a recommended value is \(|\vec{\epsilon}_{cart}| = 10^{-4}\).