It can happen that self-consistent field calculations converge to a non-global energy minimum. In such cases, it is helpful to perturb the molecular orbitals following a randomized scheme, as a different guess for the electronic density may lead to another SCF solution. Doing this can be especially important in interactive explorations of chemical reactivity or in ab initio molecular dynamics.
Scripts and source code for the orbital perturbation can be found on our github page.
A more detailed discussion of the topic, algorithm and applications can be found in doi:10.1021/acs.jctc.7b00011.