The optimization algorithm implemented in Sella has several user-tunable hyperparameters that may be passed to the Sella class. One important parameter is the iterative diagonalization convergence criterion γ, which may be set with the keyword argument gamma. By default, γ = 0.1, though tighter convergence may be requested by reducing γ. Reducing γ will result in additional iterative Hessian diagonalization steps, but will result in a more accurate approximate Hessian and therefore better subsequent geometry optimization steps. The initial trust region size 0 defaults to a value of 0.1