Relationship Between Microscopic and Macroscopic Order Parameters

Relationship Between Microscopic and Macroscopic Order Parameters 

The diamagnetic susceptibility of a single rod-like molecule can be described by two parameters and representing the molecular response to a magnetic field applied parallel and perpendicular to the molecular axis, respectively. In tensor notation the magnetic susceptibility of the molecule is given by 

From the general formalism for rotation of second rank tensors it can be shown that 

But N (C — l) is simply the macroscopic diamagnetic anistropy of the perfectly ordered nematic phase, i.e.. 

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