Complex sentence: Was a crucial step toward more realistic pseudo-potentials was given by Topp and Hopfield and more recently Cronin, who suggested that the pseudo-potential should be adjusted such that they describe the valence charge density accurately.
Split into simpler sentences: Was a crucial step toward more realistic pseudo-potentials was given by Topp and Hopfield and more recently Cronin. Who suggested that the pseudo-potential should be adjusted such that they describe the valence charge density accurately.