Latin for "from scratch" or "from first principles" Means that all results are based on solutions of Schroedinger's Equation and the wavefunction(s) used No empirical data is used
Molecular orbital Calculations which use all the molecular orbitals in a calculation, not just the valence electron orbitals Absolute configuration The way, in 3-dimensional space, in which 4 different substituents are arranged off a chiral carbon This can only be determined by X-ray Crystallography However other compounds which can be related to one with known configuration, by syntheses where there are no changes at a chiral centre, bcan also be assigned an absolute configuration