Instructions - SLD Explorer

This manual explains what each tab does, what to enter, and how to read the results. It is written as a practical guide for everyday use rather than as theory documentation.

1. General Use

What the app is for

SLD Explorer is a neutron-only desktop tool for comparing materials through nuclear and magnetic scattering length density (SLD). All values are in units of 10⁻⁶ Å⁻².

Formula syntax

• Use standard chemical formulas such as Si, Fe, H2O, D2O, Fe2O3.
• Use isotope notation like B[11]4C or Li[7]F to specify individual isotopes.
• For composition scans, use {x} and {1-x} as placeholders, e.g. Mo{x}Si{1-x}.
• For magnetic materials, enter the magnetic moment in μ_B per formula unit where the field is available.

Plot behavior

• The plot uses the built-in dark Graphite style with light labels for consistent on-screen readability.
• You can zoom and pan with the mouse.
• A crosshair follows the cursor and shows the current coordinates.
• Labels follow the data or current view dynamically as you zoom.

2. Elements & Compounds

What this tab does

This is the main tab for browsing elements and isotopes and for computing compound SLDs. The SLD plot on the right shows all elements as labeled gray circles. Selected elements and added compounds are highlighted with colored markers.

Element / Isotope browser

The text panel shows neutron data including coherent scattering length, nuclear and magnetic SLD, and incoherent cross-section.

Compound SLD calculator

• Press Calculate & Add to plot to compute the compound and add a dark green marker to the SLD plot.
• Press Clear compounds to remove previously added compound markers.

3. Composition Scan

What this tab does

This tab scans a binary composition continuously, for example from pure Si to pure Fe by stepping through Fe_xSi_1−x. It shows the trace in the complex SLD plane (Re vs Im) and produces a table of nuclear SLD at each composition step.

How to use it

• Press Scan & plot to compute and plot the composition trace. Multiple scans can be overlaid.
• Press Clear scans to remove all overlaid traces and reset the fields.

Reading the results

The plot shows the scan curve in the Im(SLD) vs Re(SLD) plane. The endpoints are labeled with the component name and composition, for example Si, x=0.00 and Fe, x=1.00. The midpoint is labeled x=0.50. The table below lists every computed composition point with its Re, Im, and incoherent SLD values.

4. SLD Search

What this tab does

This tab searches the complete element and isotope database by SLD range. Use it to find materials with a specific neutron SLD value.

Typical workflow

1. Enter a minimum and/or maximum value for real SLD, imaginary SLD, or incoherent SLD. Values are in units of 10⁻⁶ Å⁻².
2. Choose a sort order and spin channel if relevant.
3. Press Search.
4. Matching elements appear in the list, and their positions are highlighted in the SLD plot.

The Clear button resets all filters, the result list, and the plot highlighting.

5. Element Pairs

What this tab does

This tab ranks all possible element pairs by the magnitude of their nuclear SLD contrast. It gives a quick overview of which element pairs are most interesting for neutron reflectometry or diffraction experiments.

How to use it

• Select a spin channel (nuclear, spin-up, or spin-down) from the dropdown.
• Press Compute pairs to rank all element pairs.
• The table shows the top pairs sorted by |ΔSLD|.
• Click a row to highlight the corresponding pair in the SLD plot.

The info panel on the right shows detailed SLD values for the selected pair.

6. Bilayer Contrast

What this tab does

This tab computes the SLD contrast between two material layers, which is the primary quantity determining reflectometry signal strength.

How to read the result

• Nuclear SLD contrast: difference without any spin splitting.
• Spin-up / Spin-down contrast: contrast seen by polarized neutrons when the first layer is magnetic.
• The plot shows both layers as markers in the complex SLD plane.

7. Contrast Match

What this tab does

This tab answers: at what additive fraction does material A match the SLD of material B?

Important behavior

• If the Additive B formula is blank, the program reuses Additive A.
• If Additive B density is filled in explicitly, that density is respected.
• The plot shows both material SLD curves and a draggable dashed line.
• The label on the dashed line shows which A/B compositions currently match at the selected SLD.

8. Blend Explorer

What this tab does

This is a fast, slider-driven tool for intuitive two-phase SLD mixing. It is intended for real-time exploration without running a full calculation.

The bar plot updates in real time and shows how the SLD contrast changes with slider position.

Clear fields resets all input text fields in this tab.

9. Spin Contrast

What this tab does

This tab computes and visualizes |ΔSLD spin-up| versus |ΔSLD spin-down| for all element pairs. It is useful for identifying which pairs give strong spin asymmetry.

How to use it

• Choose whether to display all pairs, magnetic pairs only, or a filtered subset.
• Adjust the label threshold to control which pairs are annotated on the plot.
• Optionally enter a custom material pair to show it as a highlighted marker on the map.

How to read the map

• Pairs near the diagonal have similar contrast in both spin channels.
• Pairs far from the diagonal are strongly spin-selective, which is useful for polarized neutron reflectometry.
• The custom marker lets you compare your specific material combination to all other pairs.
• The top 20 pairs by total contrast are listed in the table at the top of the results panel. The custom pair info is shown below the table.

10. Theory and Instructions

Theory vs Instructions

• Theory (toolbar button) explains the neutron-scattering physics behind the calculations.
• Instructions (this document) explains how to operate the program tab by tab.