# Convergence Tools: mesh cutoff#

Then click on the *Parameters* icon to open the Convergence tools: mesh cutoff
parameters widget.

The project parameters that can be tuned are:

**Mesh cutoff values**in eV units. The Mesh cutoff parameter defines the plane wave cutoff for the grid. Press the**Add value**button to incorporate to the right window, each of your selected Mesh cutoff values. In this type of project, ASAP will run a set of single-point calculation using the selected Mesh cutoff values.**Directions**. You can select the direction in which you desire to evaluate the eggbox effect; 1-st, 2-nd and 3-rd unit cell vector. You must be aware that the number of calculations, and the computational time, will be doubled (tripled) when two (three) directions are selected.**Number of steps**. In this type of project, the energy is computed as a function of atomic coordinates displacement. This field indicates the number of rigid displacements.

Click on the *Calculator* icon to select the computational engine to be used
during geometry optimisation.

*Run*icon to open Run widget. Then click on the

**Run**button to submit the set of calculations required to evaluate the eggbox effect for the selected meshcutoff parameters.

*Calculator output*in Run widget shows the complete calculation output in real time.

In addition, the tab *Task output* in Run widget shows relevant information of
Geometry optimisation output in real-time.

## Analysis#

When the calculation is completed, select **Exit and analyse** to open the
analysis widget.

Select the **Convergence of the mesh cutoff…** button to visualise the
energy as a function of atomic coordinates displacement.

Check the tick-boxes corresponding to the mesh cutoff values and directions for which you desire to evaluate the eggbox effect. The maximum energy difference (\(\Delta E_{max})\) is indicated in the figure for each of the selected mesh cutoff values.

You can also visualise the effective force as a function of atomic coordinates displacement.