Molecular magnetic properties via formal annihilation of paramagnetic contribution to electronic current density

✍ Scribed by Paolo Lazzeretti; Riccardo Zanasi

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 802 KB
• Volume: 60
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/(sici)1097-461x(1996)60:1<249::aid-qua26>3.0.co;2-8

✦ Synopsis

A novel procedure for calculating magnetic susceptibilities and nuclear magnetic shieldings in molecules is outlined, based on formal annihilation of transverse paramagnetic contribution to quantum mechanical current density induced within the electron cloud by an external homogeneous, static magnetic field. Within this method all the components of nuclear magnetic shielding are independent of a gauge translation, in any calculation relying on the algebraic approximation, irrespective of size and quality of the gaugeless basis set adopted; magnetic susceptibilities are invariant for centersymmetric molecules (virtual invariance is actually observed for molecules of arbitrary symmetry). Large basis set calculations of near-Hartree-Fock magnetic properties and maps describing a current density field of acetylene molecule carried out via the new procedure are compared with corresponding ones adopting the common origin-coupled Hartree-Fock approach and methods formally annihilating the diamagnetic contribution to the current density. 0 1996 John Wiley & Sons, Inc. has always played a central role [l-51. According to the familiar theories by van Vleck [6] and Ramsey [71, theoretical magnetic susceptibilities and nuclear magnetic shieldings of a molecule are partitioned into paramagnetic and diamagnetic terms. This partition is by no means unique, as different contributions interconvert in a gauge transformation of the vector potential, leaving their sum invariant whenever certain hypervirial theorems are fulfilled [8]. Most studied gauge transforma-* This work is dedicated to Professor Roy McWeeny on the * To whom correspondence should be addressed.