Gradients calculation and search for critical points:ΒΆ

The script make_TDS_Gradients calculates the inverse gradients of the phonon dispersion relation in a specified energy window and allows for the search of critical points. The following steps must have been performed beforehand:

  • Symmetrysation
  • Fourier Interpolation
  • Debye-Waller factors for the temperature of choice

  • The usage is

    make_TDS_Gradients castep_filename input_filename

    the file castep_filename can be either the name of the original castep output our the associated hdf5 file. In any case the associated hdf5 file must exist already.

  • The input_file must set the variables:

    • Mandatories
      • subN1
      • subN2
      • subN3
      • N1
      • N2
      • N3
      • Nfour_interp
      • Temperature
      • Lambda
    • Optional
      • branchWeight
      • energyWindow
      • outputname

  • The inverse gradients of each phonon branch are written to individual .h5 and .ccp4 files. The auxilary script find_maxima.py can be used to filter the results and search for maximas,

make_TDS_Gradients.subN1 = 20

Subdivision, in the elementary brillouin zone, along the Z dimension of the reconstructed volume, which is parallel to the first axis of the brilloin zone.

make_TDS_Gradients.subN2 = 20

Subdivision, in the elementary brillouin zone, along the Y dimension of the reconstructed volume, which is parallel to the second axis of the brilloin zone.

make_TDS_Gradients.subN3 = 20

Subdivision, in the elementary brillouin zone, along the X dimension of the reconstructed volume, which is parallel to the third axis of the brilloin zone.

make_TDS_Gradients.N1 = 4

Besides being subdivised, the Brillouin zone, is replicated alonx the first axis for -N1 up to N1-1 included. In reciprocal cell vector units. N1 can be either an integer or a pair of integer. In the latter case the first element is the starting shift, the second is the ending shift+1.

make_TDS_Gradients.N2 = 4

same thing as N1 but along the second reciprocal cell vector

make_TDS_Gradients.N3 = 4

same thing as N1 but along the third reciprocal cell vector

make_TDS_Gradients.Nfour_interp = 4

The number of points in each direction of the 3D reciprocal grid. The hdf5 file must contain a previous pretreatement done with the same parameter.

make_TDS_Gradients.Lambda = 0.2

For X-ray scattering : the wavelenght in Angstroems.

make_TDS_Gradients.outputname = None

a name to design the output file with data from calculation considering branchWeight or energyWindow

make_TDS_Gradients.branchWeight = None

a list of weights : one per branch.

make_TDS_Gradients.energyWindow = None

a list of two numbers : minimum and maximum in meV