Harmonic Approximation calculations

Last updated

Jul 25, 2024

Author

Gianfranco Ulian

Harmonic approximation calculations have some minor options, mainly related to the choice of the measurement units involved and temperature settings. These options can be seen from prompting quantas ha --help or quantas ha -h.

Usage: quantas ha [OPTIONS] FILENAME

  Harmonic Approximation calculation.

  This command requires a file (FILENAME) that will be read to provide the
  input data for the calculations.

Options:
  -o, --outfile out_file          Output file where data will be stored,
                                  without extension.
  -T, --temperature min max step  Temperature range provided as a tuple.
                                  [default: ((298.15, 298.15, 1.))]
  --eunit [Ha|eV|Ry]              Measurement unit for energy values.
                                  [default: (Ha)]
  --vunit [A|bohr]                Measurement unit for volume values.
                                  [default: (A)]
  --funit [cm^-1|THz|Hz]          Measurement unit for phonon frequency
                                  values.  [default: (cm^-1)]
  --tunit [K|C]                   Measurement unit for temperature values.
                                  [default: (K)]
  -q, --quiet                     Output will not be printed on screen.
  -d, --debug                     Activate debug option.
  -h, --help                      Show this message and exit.

Define a temperature range

-T min max step, --temperature min max step

Sets the temperature range over which harmonic thermodynamic properties are calculated. This range can be set with three numbers after the flag:

• the first value represents the minimum temperature;

• the second value represents the maximum temperature;

• the third value represents the temperature step.

For example, a calculation between 400 K and 1200 K, with an increment of 0.1 K can be requested by promting:

quantas ha -T 400 1200 0.1

Note

Temperature values are float numbers.

Measurement units

--eunit EUNIT

Sets the units for energy values (default Ha). Possible choices are:

EUNIT value	Measurement unit
Ha	Hartree
eV	electronVolt
Ry	Rydberg

--vunit VUNIT

Sets the units for unit-cell volume values (default A^3). Possible choices are:

VUNIT value	Measurement unit
A^3	cubic Angstrom
bohr^3	cubic bohr

--funit FUNIT

Sets the units for (phonon) frequency values (default cm^-1). Possible choices are:

FUNIT value	Measurement unit
cm^-1	wavenumber
THz	TeraHertz
Hz	Hertz

--tunit TUNIT

Sets the units for temperature values (default K). Possible choices are:

FUNIT value	Measurement unit
K	Kelvin
C	Celsius degrees