# Property plots

The entries of the **Plot** menu draw the properties computed by CRYSTAL. The
figures are produced by [CRYSTALClear](https://github.com/crystaldevs/CRYSTALClear)
and appear in the **Plots** panel at the bottom of the window, one tab per
figure.

Some entries use the output file already open; the others read the data files
written by a properties run, and their names end with `…`. Those files are
looked for, and asked for, in the folder of the open output — see [working in
the calculation's folder](first-steps.md#working-in-the-calculations-folder).
**Plot → Plot font…** sets the font of the figures drawn afterwards.

## Electronic band structures and densities of states

**Plot → Electronic bands & DOS…** draws a band structure, a density of states,
or the two side by side.

::::{grid} 1 1 2 2
:gutter: 3

:::{grid-item}
```{image} dialog-electronic.png
:alt: The Electronic bands and DOS dialog
:class: crystal-framed
```
:::

:::{grid-item}
```{image} plot-bands-dos.png
:alt: Band structure and density of states of silicon
:class: crystal-framed
```
+++
Silicon, along Γ-X-W-L-Γ.
:::

::::

**The files.** `BAND.DAT`, `DOSS.DAT`, `*.BAND`, `*.DOSS`, `fort.25` and
`*.f25` are read. Those in the folder of the open output are listed, recognised
by their contents rather than by their names, so that a charge-density map or a
COOP file is not offered as a band structure. When a folder holds several runs,
the band file and the density of states are paired by their Fermi energy, which
identifies the SCF they come from; a disagreement is reported.

**The energies.** CRYSTAL writes them relative to the Fermi level. They can be
plotted that way or as absolute energies, in which case the Fermi energy is
added back and the line marking it moves with the data. Units are eV or
Hartree. The window is taken from the contents of the file — from the first
wide gap below the Fermi level, which separates the valence bands from the core
levels, to as far above — and **Suggested window** restores it.

**The rest.** The projections of the density of states, with their names and
colours; the treatment of the spin-down component; the labels of the path; and
the colours, styles and widths of the lines.

## Vibrational spectra

**Plot → Vibrational spectra…** lists the curves contained in the output:
infrared, Raman with its polarisations, and their anharmonic (VSCF, VCI)
counterparts where present.

::::{grid} 1 1 2 2
:gutter: 3

:::{grid-item}
```{image} dialog-spectra.png
:alt: The vibrational spectra dialog
:class: crystal-framed
```
:::

:::{grid-item}
```{image} plot-spectrum.png
:alt: Harmonic and anharmonic infrared spectra
:class: crystal-framed
```
+++
Brucite: the harmonic spectrum and its VCI counterpart, which shows the
anharmonic shift.
:::

::::

Several curves may be selected at once, which is the usual case: the
single-crystal Raman components on the same axes show the anisotropy, and a
harmonic curve under its anharmonic counterpart shows the shift. The broadening
is chosen in the same dialog — pseudo-Voigt, Lorentzian, Gaussian or a stick
spectrum — and only the widths used by the chosen lineshape are enabled.

## Anharmonic calculations

- **VCI states…** — the states of a VCI calculation, as a heatmap or a Sankey
  diagram.
- **Anharmonic scan…** — the scanned potential.
- **Anharmonic PES…** — one- and two-dimensional cuts of the potential energy
  surface, with the wavefunctions and probability densities of a double well.

## Properties read from the output

These entries use the open output file and are enabled when it contains the
data they need.

::::{grid} 1 1 2 2
:gutter: 3

:::{grid-item}

- **Elastic properties** — Young's modulus, linear compressibility, shear
  modulus and Poisson's ratio, as three-dimensional surfaces and as sections
  through them.
- **Equation of state.**
- **Phonon band structures and densities of states**, from the data files of a
  dispersion calculation.
- **Simulated XRD patterns.**

:::

:::{grid-item}
```{image} plot-elastic.png
:alt: Young's modulus surface of coesite
:class: crystal-framed
```
+++
The directional Young's modulus of coesite.
:::

::::

## Crystalline orbitals

**Plot → Crystalline orbitals…** reads the files written by the `ORBITALS`
keyword and draws the orbital in the 3D view rather than in the plot panel;
**Clear orbital** removes it.

```{image} screen2.png
:alt: A crystalline orbital across a graphite supercell
:class: crystal-framed
:width: 70%
:align: center
```

## Electron density and electrostatic potential

**Plot → Electron density & potential…** draws the grids written by `ECH3` and
`POT3` over the structure, in the 3D view; **Clear field** removes them.

::::{grid} 1 1 2 2
:gutter: 3

:::{grid-item}
```{image} dialog-density.png
:alt: The electron density and potential dialog
:class: crystal-framed
```
:::

:::{grid-item}
```{image} plot-density.png
:alt: The charge density of urea coloured by its electrostatic potential
:class: crystal-framed
```
+++
Urea: the charge density at 0.058 e/bohr³, coloured by the electrostatic
potential.
:::

::::

The CUBE files and `fort.31` are found in the folder of the open output and
recognised by their content, with the grids of the open structure offered
first. A field is drawn either as an **isosurface**, which opens at a level that
clears the drawn atoms, or on a **lattice plane** given by its Miller indices in
the conventional cell; the crystal in front of the plane is cut away and the
atoms lying in it are marked. A colour bar can be added.
A **second field** either colours the surface — the potential on the density,
as above — or is subtracted from the first.