where k is the size of the trust region at iteration k of the optimization. Note that this differs from our previous work in that the infinity-norm is used in the trust region condition, rather than the 2-norm. This is important for optimization in a redundant internal coordinate basis, as using the 2-norm would result in smaller displacements upon addition of new redundant coordinates to the coordinate system. This would unnecessarily slow optimization in systems with a high degree of redundancy in their internal coordinate system, as these redundant coordinates will result in larger displacement vectors in the 2-norm sense, but not necessarily in the infinity-norm sense.