1. A computer-based method for determining and using three-dimensional moments of molecular property fields, the method comprising the steps of: for a given molecule within a series of molecules: storing in memory first data representing a shape of the given molecule at points in a first coordinate system; storing in memory second data representing a spatial distribution of a property of the given molecule in the first coordinate system; determining a centroid of the given molecule based upon the first data; identifying a property center in the first coordinate system wherein a first order moment of the spatial distribution of the property represented by the second data is zero; and determining a displacement between the centroid and the property center.