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Generating Electric-Field Schedules with gen_eregime

This tutorial reflects the current ReaxKit generator workflow for creating eregime.in files.

What eregime.in contains

eregime.in stores sampled electric-field rows with this structure:

(iteration, V_index, direction, magnitude)

with header:

#Electric field regimes
#start #V direction Magnitude(V/A)

Main command

The general format for this command is as follows:

reaxkit gen_eregime --type <sin|pulse|func> --iteration-step <int> [profile-specific flags]

Common flags: - --output output filename/path (default eregime.in) - --direction field axis (x, y, z) - --V voltage index column - --start-iter first iteration number

Profile 1: Sinusoidal field

reaxkit gen_eregime --type sin --output eregime.in --max-magnitude 0.35 --points-per-cycle 17 --iteration-step 500 --num-cycles 2 --direction z --V 1 --copy-to-dot

Meaning: - --max-magnitude: exact positive and negative extrema around the offset - --points-per-cycle: number of rows in one complete piecewise-linear cycle, including its start and end - --iteration-step: MD iterations between consecutive rows - --num-cycles: number of complete cycles

Each cycle returns exactly to --dc-offset at its start, half-cycle, and end. Adjacent cycles share that boundary row, preventing consecutive duplicate field values. The total row count is num_cycles * (points_per_cycle - 1) + 1.

Within each quarter-cycle, the magnitude changes by an equal amount at every row. This produces linear ramps between zero and each extremum. It is therefore a triangular, piecewise-linear sampled profile rather than exact sine values. Use legacy --step-angle when exact sine-value sampling is required.

For equal-duration positive and negative halves, use an odd count such as 9 or 11. With 10 points there are nine time intervals, so one half necessarily has one additional interval.

Optional sin-only controls: - --dc-offset - --phase (must be zero or a whole multiple of 2*pi in points-per-cycle mode) - --step-angle (legacy alternative to --points-per-cycle)

Profile 2: Smooth pulse field

reaxkit gen_eregime --type pulse --output eregime.in --amplitude 0.003 --width 50 --period 200 --slope 20 --iteration-step 250 --num-cycles 5 --direction z --V 1

Meaning: - --amplitude: pulse height above baseline - --width: flat-top duration - --period: full positive+negative cycle length - --slope: rise/fall duration - --num-cycles: cycle count

Optional pulse controls: - --step-size (sampling resolution) - --baseline

Profile 3: User-defined function

reaxkit gen_eregime --type func --output eregime.in --expr "0.003*cos(2*pi*t/100)" --t-end 1000 --dt 1 --iteration-step 250 --direction z --V 1

Meaning: - --expr: function of t - --t-end: final sampled time - --dt: sampling interval - --iteration-step: iteration mapping between samples

Validation behavior

The generator validates inputs before writing: - direction must be x, y, or z - iteration_step must be positive - profile-specific required flags must be provided - pulse constraints must be physically consistent

Invalid settings raise clear errors instead of producing malformed files.

Python API note

If you need programmatic generation, the core API is:

from reaxkit.engine.reaxff.generators.eregime_generator import gen_eregime

with profile_type="sin" | "pulse" | "func" and the same profile parameters.

Output location

Generated inputs are stored using ReaxKit generator output layout (under reaxkit_workspace/inputs/), with optional --copy-to-dot to place a copy in the current working directory.

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