The energy state determines the arrangement of atoms in a molecule. Pulay realized that since atomic forces can be directly calculated, the energy minimums, and therefore the shapes, could be determined. He created computer programs and software that made this easier to do. However, his methods made it easier to determine large molecular structures containing hundreds of atoms. Pretty soon theoretical work went from a stepchild of chemistry to an essential function that is applied hand in hand with experimentation.
Structure determines function in most molecules.
You can't drive a truck if the wheels are perched on the hood, and the same philosophy applies to atom placement. Change a molecule's shape, and you get different properties and different reactions. Pulay's computational development enabled the Nobel Prize winner Pople to give extremely accurate descriptions of how chemicals react. Today Pulay's work attracts professors and students from all over the world to Northwest Arkansas, where he has been since 1982 after leaving Communist Hungary for the United States in 1980. He has won most of the major awards given to chemists in his profession, including the Alexander Von Humboldt Senior Scientist Award and membership in the International Academy of Quantum Molecular Studies, an elite group of 32 experts in the field.