GEO: How to quantify and understand errors in geometries

Nearly all electronic structure calculations contain errors in both energies and equilibrium geometries. I will show results only for molecules, but all the methodology could also be applied to materials. For molecules, quantifying errors in possibly dozens of bond angles and bond lengths is a Herculean task. Recently, we proposed the geometric energy offset (GEO) framework for quantifying and analysing errors in molecular geometries based on a single and natural measure. GEO links many disparate aspects of geometry errors: a new ranking of different methods, quantitative insight into errors in specific geometric parameters, and insight into trends with different methods. GEO can also reduce the cost of high-level geometry optimizations and shows when geometric errors distort the overall error of a method. GEO applies to all methods of simulation, including DFTB, and even classical force fields.