Molecular charge distributions in strong magnetic fields: a conceptual and current DFT study

The effect of strong magnetic fields on the charge distribution of the hydrogen halides, H (Formula presented.) O and NH (Formula presented.) is studied in the context of recent extensions of conceptual density functional theory to include additional variables such as external magnetic fields. From conceptual DFT studies on atoms in strong magnetic fields, changes in electronegativity and hardness suggest a reversal in polarity for all three diatomic molecules under these conditions. This is confirmed by current DFT calculations on these molecules in the presence of strong magnetic fields parallel and perpendicular to the internuclear axis; in the former case the electric dipole moment only undergoes small changes whereas in the latter case it changes significantly and also reverses in direction, doing so at lower field strength if the geometry is relaxed. The absence of a dipole moment induced perpendicular to the bond when a magnetic field is applied in this direction is understood by consideration of time reversal symmetry. Similar results are obtained for H (Formula presented.) O and NH (Formula presented.); this may be an important point to consider in future studies focused on the unresolved question on the behaviour of hydrogen bonding in applied magnetic fields.