compute_adf

This keyword computes the angular distribution function (ADF) for all atoms or specific triples of species. Each ADF is represented as a histogram, created by measuring the angles formed between a central atom and two neighboring atoms, and binning these angles into num_bins bins. Only neighbors with distances rc_min < R < rc_max are considered, where rc_min and rc_max are specified separately for the first and second neighbor atoms in each ADF calculation. Currently, this feature is only available for classical MD. The results are written to the adf.out file.

Syntax

For global ADF, the keyword is used as follows:

compute_adf <interval> <num_bins> <rc_min> <rc_max>

This means the ADF calculations will be performed every interval steps, with num_bins data points.

For local ADF, the keyword is used as follows:

compute_adf <interval> <num_bins> <itype1> <jtype1> <ktype1> <rc_min_j1> <rc_max_j1> <rc_min_k1> <rc_max_k1> ...

This means the ADF calculations will be performed every interval steps, with num_bins data points. The angle formed by the central atom I and neighboring atoms J and K is included in the ADF if the following conditions are met:

  • The distance between atoms I and J is between rc_min_jN and rc_max_jN.

  • The distance between atoms I and K is between rc_min_kN and rc_max_kN.

  • The type of atom I matches itypeN.

  • The type of atom J matches jtypeN.

  • The type of atom K matches ktypeN.

  • Atoms I, J, and K are distinct.

The ADF value for a bin is computed by dividing the histogram count by the total number of triples that satisfy the criteria, ensuring that the integral of the ADF with respect to the angle is 1. In other words, the ADF is a probability density function.

Example

compute_rdf 100 30 0.0 1.2 # Total ADF every 100 MD steps with 30 data points for bond lengths between 0.0 and 1.2 compute_rdf 500 50 0 1 1 0.0 1.2 0.0 1.3 # Calculate 0-1-1 ADF every 500 MD steps with 50 data points for I-J bond lengths between 0.0 and 1.2, and I-K bond lengths between 0.0 and 1.3 compute_rdf 500 50 0 1 1 0.0 1.2 0.0 1.3 1 0 1 0.0 1.2 0.0 1.3 # Calculate 0-1-1 and 1-0-1 ADF every 500 MD steps with 50 data points