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From what I understand Van der Waals (VDW) forces are the primary source of inter-molecular interaction. There are three different possible origins for van der Waals forces: permanent dipole-permanent dipole (Keesom/short range) forces, the permanent dipole-induced dipole (Debije/short range) interactions and induced dipole-induced dipole (London/long range) forces. (Here we talk about electric dipole).

We also have magnetic dipole dipole interaction which is

$\propto \frac{m_1m_2}{r^3}(3\cos^3\theta-1)$

and has quantum mechanical origins such as Pauli's exclusion principle and exchange interaction and etc.

My questions: In what cases we consider interaction between electric charge or a dipole, and magnetic dipole? i.e can magnetic dipole-dipole interaction happen along with electric dipole-dipole interaction in a systems?

Why aren't magnetic dipole-dipole forces also included alongside electric dipole-dipole forces in calculation of intermolecular forces?

Both magnetic and electric dipole dipole interactions have same origins, interpreted based on vector model mathematical formulation and these interactions happen in atomic level. When I read text books on inter-molecular forces (Israelaschvili, Cosgrov, etc), they talk about VDW electric dipole dipole interactions, non of them talk about magnetic interactions. Does it have to do with range of interaction?

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  • $\begingroup$ Oxygen molecules have a magnetic dipole moment. In the solid phase, there is antiferromagnetic ordering, but this is mostly due to the exchange interactions. The (O$_2)_2$ dimer has been studied in quantum chemistry. $\endgroup$ – Pieter Mar 14 '18 at 23:27
  • $\begingroup$ So is there any other case, that magnetic dipole-dipole forces also included alongside electric dipole-dipole forces in calculation of intermolecular forces? $\endgroup$ – Racaio Cmoto Mar 15 '18 at 6:26
  • $\begingroup$ Nice question. Here is a unconventional point of view: About the distribution of electrons magnetic dipole moments in atoms $\endgroup$ – HolgerFiedler Mar 15 '18 at 12:46
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We also have magnetic dipole dipole interaction which ... has quantum mechanical origins such as Pauli's exclusion principle ...

For me it’s a fascinating approach to establish a connection between the electrons magnetic dipole moments and Pauli’s exclusion principle. A principle does not explain the origin for a found phenomenon, it’s only stated a fact. To connect the founded phenomenon of pairwise bounded electrons with their intrinsic property, the magnetic dipole moment, is a remarkable approach.

A new area of research would be to questioning the preservation of the electric charge in atoms. I’m not talking about the compensation of the electric fields between proton and electron. I’m talking about the confluence of these fields - there neutralization - together with quantumwise emission of radiation from the merging fields and the stopp of this process near the nucleus. It would be nice to see which results would show a calculation of binding energies, based on the forces from magnetic dipole moments and the resurrected (growing up) electric field from the irradiated energy.

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