Elastic Tensor Axes![]() |
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Notes on definition of elastic tensor axesThe convention for defining elastic axes (See here for details) is that z should be along the highest order axis and x along a lower order axis if there is one normal to it. Neighbours uses the convention
for most cases. This will give the conventional definition for the elastic constants except for a few special cases. These are
Neighbours does not attempt to use the correct transformation to get the elastic axes in the conventional definition in cases (1) and (2). However in these cases the elastic constants calculated by DMAREL are correct for the axis system used; it is just not a conventional axis system. So the normal message is correct for these cases including the rhombohedral axis case. In case 3) Neighbours does move the x axis so that it lies along the 2 fold axis (if there is one) rather than being normal to it. This is the only case for which the normal definition does not apply. What I would suggest doing is either
Eventually we should modify neighbours to allow for cases 1) and 2)
and at this point we may need to modify what is Maurice Leslie, 17 October 2005 | |||
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