# hfc_display.m

Draws hyperfine tensors and their eigensystems. Two styles are implemented:

A. Ellipsoids (symmetric tensors only)
1. A unit sphere in a Cartesian space is scaled by abs(Axx) in the x direction, abs(Ayy) in the y direction and abs(Azz) in the z direction, where Axx, Ayy, Azz are the eigenvalues of the HFC tensor in units of milliTesla.
2. A set of axes is drawn inside the sphere with a red axis for a positive eigenvalue, and a blue axis for a negative one.
3. The sphere is translated to the point of corresponding nucleus and rotated into the molecular frame of reference.
B. Spherical harmonics (default)
1. The matrix is converted into irreducible spherical tensor operator coefficients.
2. The coefficients are placed in front of the corresponding spherical harmonics, which are plotted in three dimensions and translated to the point of the corresponding nucleus.

## Syntax

    hfc_display(props,atoms,scaling,conmatrix,options)


## Arguments

              props - output of gparse.m function

atoms - a cell array of element symbols,
indicating the atoms for which
the hyperfine tensors should be
visualised, e.g. {'C','H'}

scaling - a factor to scale the tensors
by for visualisation

conmatrix - binary connectivity matrix, 1
if a pair of atoms should be
connected by a bond. If an em-
pty vector is supplied, 1.6
Angstrom cutoff distance is used

options.style - 'ellipsoids' or 'harmonics'

options.kill_iso - set to true() to eliminate the
isotropic parts of tensors be-
fore plotting


## Examples

The following figure is produced by /examples/visualisation/hfc_pyrene.m - (left) ellipsoid plot; (right) spherical harmonic plot.

## Notes

Only Gaussian quantum chemistry package is supported at the moment - send an email to Ilya Kuprov if you are using something else.