# efg_display.m

Draws electric field gradient 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 CST tensor in units of ppm.

- 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

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

## Arguments

props - output of c2spinach.m function atoms - a cell array of element symbols, indicating the atoms for which the EFG tensors should be visu- alised, e.g. {'N','O'} 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/efg_silicate.m - (left) ellipsoid plot; (right) spherical harmonic plot.

## Notes

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

## See also

hfc_display.m, cst_display.m, volplot.m, molplot.m, conmat.m, gparse.m

*Version 2.7, authors: Ilya Kuprov*