GeomeTRIC uses a wrapper around QUICK, which is unlike DL-FIND as shown in Figure . Cartesian coordinates are used as input by GeomeTRIC, which transforms them to internal coordinates for optimization. After each cycle of optimization, it updates its own Hessian estimate using the BFGS algorithm. In order to generate an input file for QUICK to obtain the energy and Cartesian gradient, internal coordinates are converted to Cartesian coordinates at the end of each cycle. The Cartesian gradient from QUICK is used to calculate the internal coordinates gradient followed by Hessian update to estimate the search direction and step size.