How can we examine convergence of the total energy a system with respect to the meshcutoff?

The **MeshCutOff** controls the accuracy in the calculation of some integrals in real space. It is no a variational parameter in the sense that more accurate does not mean lower energy.

The way to converge it is just by making it larger and larger until the property you are interested in is converged within the tolerance you need.

Property like e.g. total energy, the effect of atom displacement, changing magnetic configuration, imposing pressure, etc.