All options and parameters related to the convergence behavior of the SCF are defined in this block key. Also the finite temperature distribution is part of this. See also second list.
Criterion for termination of the SCF procedure. Default depends on Accuracy, for instance 3e-4 for Accuracy 4.0
(Slabs only) Requires a numerical argument, which is an energy width, in a.u.. It simulates a finite-temperature electronic distribution. By default, zero temperature is assumed. The key may be used to achieve convergence in an otherwise problematically converging system (slabs, typically). The energy of a finite-T distribution is different from the T=0 value, but for small T a fair approximation of the zero-T energy is obtained by extrapolation. The extrapolation energy correction term is printed with the survey of the bonding energy in the output file. Check that this value is not too large. Build experience yourself how different settings may affect the outcomes. Remember that this key is meant to help you overcome convergence problems, not to do finite-T research: only the electronic distribution is computed T-dependent, other aspects are not accounted for!
Smooths (slightly) occupation numbers around the Fermi level, so as to insure that nearly-degenerate states get (nearly-) identical occupations. Default=off, but in case of problematic SCF convergence the program will turn this key on automatically, unless the key Nodegenerate is set in input. The smoothing depends on the argument to this key, which can be considered a 'degeneration width'. When the argument reads 'default', the program will use a default value for the energy width (1e-4).
