[Chimera-users] Principal axis of inertia
Tom Goddard
goddard at cgl.ucsf.edu
Fri Mar 21 23:55:22 PDT 2008
Oops. That script I posted for calculating the inertia of a molecule
had some problems. The printed matrix of axes was transposed though the
correct axes were used for the displayed ellipsoid. Also I was using
inertia matrix I_ij = sum_over_k(m_k*r_ki*r_kj) omitting the diagonal
term. Should have been I_ij = sum_over_k(m_k*(|r_k| - r_ki*r_kj)). And
finally I incorrectly computed the ellipsoid size along each axis.
Everything was a little bit wrong. Here's the fixed version. Tested in
Chimera version 1.2500 but should work with earlier versions.
Tom
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