Xtal-xplore-R: a graphical tool for exploring the residual function involved in crystal structure determination

This work presents Xtal-xplore-R, a tool dedicated to the visualization of two-dimensional cuts through the multidimensional crystallographic residual function. It imports arbitrary crystal structures, generates artificial diffraction data, and calculates and investigates the residual function in parameter space. The program serves two major purposes. Firstly, it is part of a more general project dealing with structure determination via global optimization techniques. In this context, the tool is being used to systematically analyse characteristic universal features of the target function (residual function) which can be used to develop appropriate problem-specific heuristic optimization algorithms. Secondly, Xtal-xplore-R is intended as a didactic tool to visualize how changes in atom parameters affect the residual function and can be used to demonstrate manual structure optimization for simple crystal structures.