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Growth Rate Analysis Walkthrough

This tutorial demonstrates how to analyse how a crystal grows over time using CrystoGen simulation output.

Prerequisites

  • A folder of CrystoGen output containing:
  • Multiple XYZ files (one per time step, or a size.csv file)
  • A simulation parameters file listing crystallographic directions
  • CGAspects is open

Step 1 — Load the Data

  1. Click Import XYZ Files and select your simulation folder
  2. CGAspects scans for size files and detects available directions
  3. If a size file is found, the Calculate Growth Rates button becomes active

Note

If only XYZ files are present (no size.csv), CGAspects can still estimate sizes from the point cloud extents. The analysis options will reflect what data is available.

Step 2 — Start Growth Rate Analysis

  1. Click Calculate Growth Rates in the left panel
  2. The Growth Rate configuration dialog opens

Step 3 — Configure the Analysis

Select Directions

Check the directions you want to analyse from the scrollable list. These correspond to the crystallographic directions defined in your CrystoGen simulation.

For a first look, check all available directions.

Choose X-Axis Mode

Mode When to Use
Auto Default — uses time column if available, otherwise row index
Force time If you know a time column is present and want an error if missing
Row index To use frame number rather than simulation time

Leave as Auto for most cases.

Click OK

The analysis starts. A progress bar shows computation progress.

Step 4 — View Results in the Plotting Dialog

When analysis completes, the plotting dialog opens with growth rate results.

  • X axis: Time (or row index)
  • Y axis: Crystal dimension along each direction
  • Each direction is plotted as a separate series

Add a Trendline

  1. Click Trendline in the plotting toolbar
  2. Select Linear fit or Polynomial fit
  3. The fitted line and equation appear on the plot

The slope of the linear fit gives the average growth rate (Å/time unit).

Step 5 — Apply Smoothing

If your data is noisy:

  1. Click Smoothing in the plotting toolbar
  2. The Smoothing dialog opens — one tab per data series
  3. For each series, choose:
  4. Method: Savitzky-Golay is a good default (preserves peaks)
  5. Window size: Larger window = more smoothing (try 11–21)
  6. Click Apply

The smoothed data overlays the original. Use the Legend Display Mode to show both or just the processed series.

Step 6 — Compare Directions

To compare growth along different directions:

  1. In the plotting dialog, use Colour by to map direction names to different colours
  2. Or generate separate plots for each direction using the permutation mode

Directions that grow faster have steeper slopes on the size-vs-time plot.

Step 7 — Export

  • Save plot: Click Save in the navigation toolbar
  • CSV data: aspects_output/growth_rates.csv contains all size vs time data
  • Render: Press Ctrl+R to save a 3D viewport snapshot of any frame

Interpreting the Results

Observation Interpretation
Steep slope Fast growth along that direction
Shallow slope Slow growth (kinetically limited)
Plateau Growth stopped (equilibrium reached)
Nonlinear curve Growth rate changes over time (e.g., due to supersaturation depletion)

For the scientific background on how growth rates relate to crystal morphology, see Zingg Classification.