check_momentum

Command Line Tool for Checking the Total Linear Momentum

This command line tool can be used to calculate the norm of the total linear momentum P = sum_i m_i * v_i of (a selection of) atoms for every frame of a velocity trajectory. It can be used to check a simulation for center of mass drift.

For every frame one row containing the one-based frame index and the scaled momentum norm is written. With velocities in Angstrom/s (PQ velocity trajectories) the default scaling factor of 1e-15 converts the momentum norm from amu*Angstrom/s to amu*Angstrom/fs.

Note that the velocities are parsed from file in single precision, so reported norms below roughly 1e-7 * sum_i m_i * |v_i| * scale are parsing noise, not physical center of mass drift. The legacy equipartition.jl tool parses the velocities in double precision and therefore resolves correspondingly smaller drift for momentum-conserving trajectories.

Summary

Classes:

CheckMomentumCLI

Command Line Tool for Checking the Total Linear Momentum

Functions:

main	Main function of the check_momentum command line tool, which is basically just a wrapper for the check_momentum function.

Reference

class CheckMomentumCLI

Bases: CLIBase

Command Line Tool for Checking the Total Linear Momentum

classmethod add_arguments(

parser: _ArgumentParser,

) → None

Adds the arguments to the parser.

Parameters:

parser (_ArgumentParser) – The parser to which the arguments should be added.

classmethod program_name() → str

Returns the name of the program.

Returns:

The name of the program.

Return type:

str

classmethod run(args)

Runs the command line tool.

Parameters:

args (argparse.Namespace) – The arguments parsed by the parser.

main()

Main function of the check_momentum command line tool, which is basically just a wrapper for the check_momentum function. For more information on the check_momentum function please visit PQAnalysis.analysis.momentum.api.check_momentum().