SAM computes the symmetry adapted modes in the Γ point and classifies them by their infrared,
Raman and Hyper-Raman activity. This document explains step by step how the program can be used.
There are two different options to use the program:
OPTION A: Space group
One has to introduce the space group number and select the Wyckoff positions occupied by the atoms in the structure.
The program classifies the symmetry adapted modes in IR, Raman and Hyper-Raman modes.
Moreover, there are shown which are the allowed second order IR and Raman modes. On the other
hand, there is also available information about the point group such as character's table,
irreps decomposition and selection rules.
OPTION B: Structure
One can introduce the structure data using a CIF file or filling the appropiate field, which should include:
The number of the space group as given in the International Tables for Crystallography, Vol. A (ITA)
The lattice parameters
The number of independent atoms
The independent positions of the atoms, including the labels, a sequential number, the Wyckoff positions (if they are unknown it is sufficient to use a dash "-" instead) and the atomic coordinates relative to the lattice parameters
The program shows the classification of the symmetry adapted modes and the total number of
IR, Raman and Hyper-Raman active modes.
Some notes for the correct use of the program SAM:
In the step 1 of the input data there is a link of a table with all
space group ITA numbers with the avaliable settings.
The irreps - irreducible representations - are written in Millikan notation.
For the users of the program REPRES the output of this irreps are written in the
same order of SAM are, in the special case of Γ point.
The symmetry adapted modes are calculated by the projection operator method and they are expressed in an orthoghonal basis.
One hase to introduce the structure, one can do it directly using the following format:
# Comments start with #
# Space Group ITA number
# Lattice parameters
4.7597 4.7597 12.9935 90 90 120
# Number of independent atoms in the asymmetric unit
# [atom type] [number] [WP] [x] [y] [z]
Al 1 12c 0.0000 0.0000 0.3523
O 1 18e 0.3065 0.0000 0.2500
Or one can introduce the CIF file in the program.
In the first part of the output one can find the information about the mechanical representation of the introduced structure.
After this one can find the selection rules for the structure, the IR, Raman and Hyper-Raman active modes.
The number of IR, Raman and Hyper-Raman active modes of the structure are given and one can also find the information about the acustic modes.