Velocity¶

class py4vasp.data.Velocity(*args, **kwargs)¶

Bases: Mixin, Refinery, Mixin

The ion velocities for all steps of the calculation.

The velocities are only stored if you set VELOCITY = T in the INCAR file. You can read velocities of different steps see the examples below.

Examples

If you access a method of this class, the result will depend on the steps that you selected with the [] operator. Without any selection the results from the final step will be used.

>>> calc.velocity.read()

To select the results for all steps, you don’t specify the array boundaries.

>>> calc.velocity[:].read()

You can also select specific steps or a subset of steps as follows

>>> calc.velocity[5].read()
>>> calc.velocity[1:6].read()

Attributes Summary

path	Returns the path from which the output is obtained.
velocity_rescale

Methods Summary

from_data(raw_data)	Create the instance directly from the raw data.
from_file(file)	Read the quantities from the given file.
from_path([path])	Read the quantities from the given path.
plot()	Plot the velocities as vectors in the structure.
print()	Print a string representation of this instance.
read(*args, **kwargs)	Convenient wrapper around to_dict.
to_dict()	Return the structure and ion velocities in a dictionary

Attributes Documentation

path¶

Returns the path from which the output is obtained.

velocity_rescale = 200¶

Methods Documentation

classmethod from_data(raw_data)¶

Create the instance directly from the raw data.

Use this approach when the data is put into the correct format by other means than reading from the VASP output files. A typical use case is to read the data with from_path and then act on it with some postprocessing and pass the results to this method.

Parameters:

raw_data – The raw data required to produce this Refinery.

Return type:

A Refinery instance to handle the passed data.

classmethod from_file(file)¶

Read the quantities from the given file.

You want to use this method if you want to avoid using the Calculation wrapper, for example because you renamed the output of the VASP calculation.

Parameters:

file (str or io.BufferedReader) – Filename from which the data is extracted. Alternatively, you can open the file yourself and pass the Reader object. In that case, you need to take care the file is properly closed again and be aware the generated instance of this class becomes unusable after the file is closed.

Returns:

The returned instance handles opening and closing the file for every function called on it, unless a Reader object is passed in which case this is left to the user.

Return type:

Refinery

Notes

VASP produces multiple output files whereas this routine will only link to the single specified file. Prefer from_path routine over this method unless you renamed the VASP output files, because from_path can collate results from multiple files.

classmethod from_path(path=None)¶

Read the quantities from the given path.

The VASP schema determines the particular files accessed. The files will only be accessed when the data is required for a particular postprocessing call.

Parameters:

path (str or pathlib.Path) – Path to the directory with the outputs of the VASP calculation. If not set explicitly the current directory will be used.

Returns:

The returned instance handles opening and closing the files for every function called on it.

Return type:

Refinery

plot()¶

Plot the velocities as vectors in the structure.

This is currently only implemented for a single step. So selecting multiple steps will raise an error.

Returns:

Contains all atoms and the velocities are drawn as vectors.

Return type:

Viewer3d

Examples

If you access this method, the result will depend on the steps of the class that you selected with the [] operator. Without any selection the results from the final step will be used.

>>> calc.velocity.plot()

To select the results for all steps, you don’t specify the array boundaries.

>>> calc.velocity[:].plot()

You can also select specific steps or a subset of steps as follows

>>> calc.velocity[5].plot()
>>> calc.velocity[1:6].plot()

print()¶

Print a string representation of this instance.

read(*args, **kwargs)¶

Convenient wrapper around to_dict. Check that function for examples and optional arguments.

to_dict()¶

Return the structure and ion velocities in a dictionary

Returns:

The dictionary contains the ion velocities as well as the structural information for reference.

Return type:

dict

Examples

If you access this method, the result will depend on the steps of the class that you selected with the [] operator. Without any selection the results from the final step will be used.

>>> calc.velocity.to_dict()

To select the results for all steps, you don’t specify the array boundaries.

>>> calc.velocity[:].to_dict()

You can also select specific steps or a subset of steps as follows

>>> calc.velocity[5].to_dict()
>>> calc.velocity[1:6].to_dict()