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Materials database: Part A - Introduction

This page explains what’s in the OghmaNano Materials database, how to open and edit entries, how to import n–k or absorption data (including unit conversion), and where materials are stored on disk.

1. Overview

The OghmaNano Materials database stores a range of physical and reference properties for each material. These are organised into categories so that simulations can use consistent, centralised data. The main information includes:

Together, these datasets provide a central, consistent definition of each material for use across all simulations.

OghmaNano Material editor showing refractive index of the material as a function of wavelength
Refractive index vs. wavelength
OghmaNano Material editor showing absorption spectrum of the material as a function of wavelength
Absorption spectrum vs. wavelength
OghmaNano Material editor showing optical emission spectrum of the material as a function of wavelength
Optical emission spectrum vs. wavelength
OghmaNano Material editor showing basic parameters including material color, type, privacy options, and change log
Basic parameters: color, type, and change log
OghmaNano Material editor showing stored electrical parameters for the material. These are reference values and not directly used in simulation.
Stored electrical parameters (reference only)
OghmaNano Material editor showing thermal parameters such as conductivity and carrier relaxation times
Thermal parameters
OghmaNano Material editor showing life cycle parameters including density, cost per kilogram, and energy per kilogram
Life cycle parameters: density, cost, and energy per kg

2. Accessing the materials database

Open the Materials Database from the Databases ribbon by clicking the Materials Database icon ??. This launches the Materials Database browser ??, which shows top-level folders alongside individual materials represented by “atom” icons. Double-click a folder to explore the structured library—organised by material class (e.g., metals, oxides, glasses) and including a dedicated collection imported from refractiveindex.info. Click an atom icon to open that material’s property views described above. Use Help for guidance, and Add Material to create a new entry or import your own datasets.

Databases ribbon in OghmaNano with the Materials database icon highlighted—the entry point for opening the materials database
Accessing the Materials database from the Databases ribbon
Initial Materials database browser view showing top-level material categories, address bar, Add Material, and Help buttons
Initial view of the Materials database (top-level categories)

3. Adding materials to the database

To add a new material open the Materials database, then click add material in the top right of the window (??), this will bring up a dialogue box which will ask you to give a name for your new material, this is visible in figure ??. In this case we called the material my_new_material.

OghmaNano Materials database window showing the Add Material button highlighted
Adding a new material to the Materials database using the Add Material button.
Dialog window in OghmaNano prompting for a new material name, with example 'my_new_material'
Naming a new material in the Materials database dialog.

Once you have clicked OK the new material will appear see Figure [fig:materialadd4], open it by double clicking on it. This will bring up an empty material window with no data. See Figure [fig:materialadd5].

OghmaNano Materials database window showing the newly created material 'my_new_material' highlighted in red
The new material my_new_material added to the Materials database.
OghmaNano Material editor window for a newly created material, showing empty data tabs for Absorption, Refractive index, Basic, Electrical parameters, and Thermal parameters
The Material editor window for the newly created material my_new_material, initially empty of data.

4. Understanding n/k data (n/alpha data)

Before try to add n/k (n/alpha data) to OghmaNano , it’s important to understand what n–k data is. n–k data describes the complex refractive index of a material: the real part n and the imaginary part k.

There are several ways you will see optical loss written in the literature. Common forms include the absorption coefficient α (loss per metre, units m−1), the extinction coefficient k (the imaginary part of the refractive index, dimensionless), and absorbance (also called optical density), which is a logarithmic measure of transmission typically used in spectroscopy. It’s important to note that these are all the same physical quantity in principle, just expressed in different forms. OghmaNano accepts the absorption coefficient α in units of m−1. The box below explains the differences between these quantities and how to convert between them.

n, k, and absorption α — at a glance

The complex refractive index is \( N(\lambda) = n(\lambda) + i\,k(\lambda) \), where \(n\) (refractive index) and \(k\) (extinction coefficient) are dimensionless. OghmaNano stores:

If you have \(k(\lambda)\) instead of \( \alpha(\lambda) \), the importer converts using: \( \displaystyle \alpha(\lambda) = \frac{4\pi\,k(\lambda)}{\lambda} \) (with \( \lambda \) in metres → \( \alpha \) in \( \mathrm{m^{-1}} \)).

From absorbance/optical density (A) or transmittance (T)
  • \( A = -\log_{10}(T) \)
  • \( \displaystyle \alpha = (\ln 10)\,\frac{A}{d} \) where \( d \) is film thickness (m)

Units to use: \( \lambda \) in metres (m); \(n\) and \(k\) are dimensionless; \( \alpha \) in \( \mathrm{m^{-1}} \). Curves labelled “a.u.” for absorption cannot be used directly.

Worked example — convert \(k \rightarrow \alpha\)

Given \( k=0.02 \) at \( \lambda=500\,\mathrm{nm}=5.00\times10^{-7}\,\mathrm{m} \):

\( \displaystyle \alpha = \frac{4\pi k}{\lambda} = \frac{4\pi \times 0.02}{5.00\times10^{-7}} \approx 5.03\times10^{5}\ \mathrm{m^{-1}} \).

5. Importing n/alpha data (or n/k data)

Click Import data from file at the top-left of the material window ?? to open the Import Data wizard ??. If you have the Refractive Index tab open, when you click Import Data from File, the data will be imported into the refractive index dataset. If you have the Absorption tab selected, it will be imported into the absorption dataset. Make sure you import the right data into the right tab. The wizard loads your file, maps its columns, and converts units to the format OghmaNano uses.

Expected file formats (two columns, SI):

If your source uses other units (e.g. nm, μm, cm−1, or eV for photon energy), the wizard converts them (e.g. nm → m, cm−1 → m−1, eV → m via λ = hc/E). If your file has k(λ), the wizard can also compute absorption using α(λ) = 4πk(λ)/λ.

Workflow:

  1. Open your text/CSV file.
  2. Check the preview (left panel).
  3. Select the x-axis units (wavelength) and the y-axis quantity (n, k, or α) and units. These need to match the units on your input data
  4. For k choose ""
  5. Review the converted SI data (right panel).
  6. Click Import data to save it to the material.

The wizard view is shown in ??; after import, the plots update in the material editor ??. If you import only absorption, remember to also provide refractive index before using the material in a simulation.

OghmaNano data importer window showing steps to import material data with labelled regions a) to f)
The Data importer window in OghmaNano, showing the workflow for importing material data: a) open data file, b) preview of the imported file, c) select x-axis units, d) select y-axis units, e) converted file in SI units, f) import the data.
OghmaNano Material editor showing imported absorption spectrum data for my_new_material
The imported absorption spectrum

Common pitfalls

  • Absorption in “a.u.” or normalised to 1 → not usable, as it has lost its magnitude information..
  • The final imported values will be in SI units, look at them - do they make sense - do a ballpark magnitude check?

👉 Next step: Now continue to Part B for tips on finding n/k data for your material system.