The quantum mechanical relativistic calculations

In the periodic table of the elements there are 106
entries: every atom is identified by the number of protons
(atomic number) contained in the nucleus. When the atomic
number is increased, the nuclear charge increases too,
augmenting the attraction between the nucleus and the
electrons and therefore these last ones improve their
speed, which value becomes comparable with the light speed.

In this case the Schroedinger equation is inappropriate
and the one of Dirac, which takes into account relativistic
effects, must be used. This correction is necessary for about
half of the elements of the periodic table, therefore molecules
with heavy atoms must be described by this methodology.

For more informations send a mail to:
Lorenzo Pisani
Bibliography:
 E. Clementi, L. Pisani, "DiracFock SelfConsistent Field
Calculations for ClosedShell Molecules with Kinetic Balance",
, in METECC94, Methods and Techniques in Computational Chemistry",
vol. A, E. Clementi ed., STEF, Cagliari (1993).