Quantization: means that a quantity does not vary continuously. The energy of an electron in an atom cannot have any arbitrary value but only certain characteristic values. A definite quantum of energy is accepted while moving from lower to higher energy level or lost while moving from higher to lower energy level, It does not
adiabatic approximation An approximation used in quantum mechanics when the time dependence of parameters, such as the internuclear distance between atoms in a molecule, is slowly varying. This approximation means that the solution of the Schrodinger equation at one time goes continuously over to the solution at a later time. It was formulated by Max
A method of calculating atomic and molecular structure directly from the first principles of quantum mechanics, without using quantities derived from experiment (such as ionization energies found by spectroscopy) as parameters. Ab-initio calculations require a large amount of numerical computation; the amount of computing time required increases rapidly as the size of the atom or molecule