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euphonic-optimise-dipole-parameter

This program is useful for users wanting to efficiently calculate phonon frequencies on many q-points for polar materials.

Polar materials have a long range force constants matrix, so an analytic correction must be applied, which is computationally expensive. The correction is calculated using an Ewald sum, and the balance between the real and reciprocal sums can be tuned to reduce the computational cost without affecting the result. This is done with the dipole_parameter argument to :py:meth:`ForceConstants.calculate_qpoint_phonon_modes <euphonic.force_constants.ForceConstants.calculate_qpoint_phonon_modes>`

The program runs a calculation for a small test number of q-points (100 by default) repeatedly for different values of dipole_parameter, and times both the initialisation time, and time per q-point. Euphonic precalculates as much of the correction as it can to minimise the calculation time per q-point, so although some dipole_parameter values will have higher initialisation time, the time per q-point may be lower, which is what's important when calculating for many q-points.

Usage

Simply run the program on a .castep_bin file to get an output suggesting the optimum dipole_parameter. For example, for quartz.castep_bin:

euphonic-optimise-dipole-parameter quartz.castep_bin

Results for dipole_parameter  0.25
Ewald init time     :  0.39 s
Ewald time/qpt      :  27.69 ms

Results for dipole_parameter  0.50
Ewald init time     :  0.08 s
Ewald time/qpt      :  5.57 ms

Results for dipole_parameter  0.75
Ewald init time     :  0.03 s
Ewald time/qpt      :  4.17 ms

Results for dipole_parameter  1.00
Ewald init time     :  0.03 s
Ewald time/qpt      :  6.79 ms

Results for dipole_parameter  1.25
Ewald init time     :  0.06 s
Ewald time/qpt      :  10.30 ms

Results for dipole_parameter  1.50
Ewald init time     :  0.06 s
Ewald time/qpt      :  15.04 ms

******************************
Suggested optimum dipole_parameter is  0.75
init time           :  0.03 s
time/qpt            :  4.17 ms

As you can see above, the time per q-point has been reduced from 6.79ms per q-point to 4.17ms per q-point, just by correctly tuning the real and reciprocal sums.

You can change the number of q-points to test, the minimum dipole_parameter, maximum dipole_parameter, and step size between dipole_parameter values. To see the command line options, run:

euphonic-optimise-dipole-parameter -h

Or see the command line options in more detail below

Command Line Options

.. argparse::
   :module: euphonic.cli.optimise_dipole_parameter
   :func: get_parser
   :prog: euphonic-optimise-dipole-parameter