Mike Glazer’s Programs

NOTE: Users prior to April 11th 2013 should download Version 2.7, as several bug fixes have been made.


VIBRATE! is a program, written by Professor Mike Glazer (Oxford University) to run on Microsoft Windows, in order to compute the irreducible representations for normal modes of vibration  and magnetic modes directly from a crystal structure using Factor Group Analysis. The default is to carry out the analysis for modes at the centre of the Brillouin Zone (k = 0) and as such is ideal for spectroscopy applications such as Raman or Infra-Red Spectroscopy. Operation of the program is very simple. It is first necessary to input the crystal structure and once this is done the program automatically computes the rest.

Input of the crystal structure is done by specifying a space group and the positions of the atoms. Alternatively input is immediate using a Crystallographic Information File (CIF), the usual way that crystal structure information is available these days.

Note that in Windows 7 you should use Compatibility Mode for XP. The latest Version2.5 now has VRML structure plotting installed. Read Help File for details to enable this to work.


Below is shown a typical screen view for the tetragonal form of BaTiO3, showing that the irreducible representations are 4A1+B1+5E in point group 4mm (C4v).


The direct output also lists the invariances  for IR and Raman selection rules for the relevant irreducible representations.

In order to enter atoms manually, this is done through a simple dialog box (left).


 

In addition, character projection operators can be listed enabling the symmetry-adapted vectors to be drawn on a crystal structure diagram.

For example, in the case of BaTiO3,  the T2u (5-) irreducible representation  leads to the following symmetry-adapted vectors:


 

We see from this that only the oxygen atoms are involved in motion corresponding to this irreducible representation. For example, the y movement of O1 is opposite to the y movement of O3 (first line), the z movement of O1 is opposite to the z movement of O2 (second line), and the x movement of O2 is opposite to the x motion of O3 (third line).


Another selectable feature repeats the calculations atom by atom so you can then see which atomic movements contribute to which irreducible representations. In addition, a button is available to enable the computation to switch to magnetic modes.


For solid-state specialists, there is also a facility to derive the irreducible representations for normal modes at k ≠ 0.


A short paper describing the program  has recently been published in J. Appl. Cryst. (doi:10.1107/S0021889809040424). If you would like to obtain a copy of VIBRATE!  click here. In addition, you can download a PDF of the Help File which contains more details about the program and how to use it. Any problems then please email Mike Glazer.

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