# Plotting Absorbance Spectra

`orto` can plot absorbance spectra, with similar features to `orca_mapspc`.

## Usage

To plot an absorbance spectrum run


::: {code-block} bash
    orto plot abs <output_file>
:::

where `<output_file>` is the path to your _ORCA_ output file containing at least one  `ABSORPTION SPECTRUM VIA ...` table.

The plot will be displayed on screen, and will be saved as a PNG file in the current working directory - both of these features can be disabled using optional arguments.

The plot data (spectrum and individual transitions) can also be saved as CSV files using the equivalent `orto gen abs` command - this has exactly the same functionality as `orto plot abs`, but saves the data instead of plotting it.

## Intensities

Several different intensity types can be plotted, controlled using the `--intensities` optional argument. The available intensity types are:

- `velocity` - Velocity Electric Dipole Moment
- `electric` - Length Electric Dipole Moment
- `semi-classical` - Oscillator Strength

## Font and Figure Size

`orto plot abs` prints the figure width to the terminal in both inches and centimetres, to help with inclusion in documents - simply set the size of the figure in your document to match the printed width to ensure the figure is not resized and the font sizes remain correct.

The default font is [DejaVu Sans](https://dejavu-fonts.github.io/), which is a free, open-source font with good Unicode support. This can be changed using the environment variable `orto_fontname`.

The default font size is 10 pt, with 9 pt for legend entries. This cannot be changed by users at present.

## Optional Arguments

Additional command line arguments for `orto plot abs` can be listed by running


::: {code-block} bash
    orto plot abs -h
:::

## Example

The following example `orca` input file contains a TDDFT calculation for the 50 lowest electronic excited states of a Pt(dcbpy)Cl₂ complex, using the CAM-B3LYP functional and the def2-TZVP basis set. The geometry is read from an external XYZ file.


:::::{tab-set}

::::{tab-item} `pt_dcbpy_cl2.inp`
:sync: tab1

::: {code-block} text
!cam-b3lyp def2-tzvp rijcosx def2/j verytightscf defgrid3

%tddft
DoNTO true
nroots 50
tda false
end

%maxcore 4000
%pal nprocs <NUMBER_OF_CORES> end

*xyzfile 0 1 pt_dcbpy_cl2.xyz
:::
::::

::::{tab-item}  `pt_dcbpy_cl2.xyz`
:sync: tab2

:::{code-block} text
29
B3LYP/def2-svp optimised Pt(dcbpy)Cl2
Pt         -2.10603723309141     -1.76139999377800      0.32205362234843
Cl         -4.41146227455970     -1.74669241619429      0.59697475529693
Cl         -2.10502179010104     -4.07582785465096      0.13756110796290
C          -2.92456217882701      1.13988690089701      0.65062207372897
C          -0.63244000642289      0.73989264236506      0.34551474696291
C          -2.71401174780175      2.51294008880245      0.73472938758467
H          -3.91318337839179      0.67851052162085      0.73175739192977
C          -0.36073666450322      2.10693050213438      0.42179521760283
C          -1.40917027638643      3.00949437876495      0.61858971113023
H          -3.55847109644971      3.18495505823491      0.88885539548731
H           0.65432836027357      2.49419182748761      0.33159492915462
C           0.77883299892454     -2.60066522154205     -0.08790595343008
C           0.39419252942759     -0.29704233435440      0.14077405262814
C           2.14768217690127     -2.39755277969848     -0.23510866447774
H           0.31334496812201     -3.59042133658750     -0.11094267016631
C           1.75742601245953     -0.03249617221899     -0.00082029308278
C           2.65009790957734     -1.09052050048040     -0.19131688315613
H           2.81194252190957     -3.24940530712368     -0.38198971711096
H           2.14924382000374      0.98425712170685      0.03317701336020
N          -0.07582640025161     -1.57715423222968      0.09523034774620
N          -1.91028163996228      0.27569810380746      0.46093974683498
C          -1.07834619448940      4.46892909009037      0.69525373896754
O           0.04082816748130      4.90968614676852      0.59668424345169
O          -2.16492863365871      5.23430307880316      0.88597304353264
H          -1.86568467867244      6.15929105898222      0.92393557221495
C           4.10571488906422     -0.76716565695724     -0.33927290512918
O           4.55146554538252      0.35377948418698     -0.30287927045076
O           4.86147128139122     -1.86262870731143     -0.51709958926730
H           5.78459301265098     -1.56777348652571     -0.60368014865466
:::
::::

:::::


The output of this calculation can be used with `orto plot abs` to generate an absorbance spectrum


::: {code-block} bash
    orto plot abs pt_dcbpy_cl2.out
:::

By default, `orto` will use an x-axis with units of electron volt (eV), but this can be changed using the `--x_unit` optional argument - for example, to plot the spectrum with an x-axis in nanometers (nm), run


::: {code-block} bash
    orto plot abs pt_dcbpy_cl2.out --x_unit wavelength
:::

or to plot with wavenumbers (cm⁻¹) on the x-axis, run


::: {code-block} bash
    orto plot abs pt_dcbpy_cl2.out --x_unit wavenumber
:::

Additional optional arguments for `orto plot abs` can be listed by running


::: {code-block} bash
    orto plot abs -h
:::