1. Open the database repres and compute the adjacency matrix for the α-SrSi₂ structure. What AutoCN method should you use? Be sure that Solid Ang. and Dist. + Rsds options are checked. After the calculation close the AutoCN window and look at the adjacency matrix. Are there differences between distances and solid angles (SA) for different bonding? The solid angles as well as interatomic distances are the parameters of relative strength of interatomic bonds; the larger is the value for the solid angle, the stronger is the bond.
   
   





2. Open Compound/Generate Representations window and click Ok. Specify the name repres_all to create a new database with different representations of the structure.
   
   



3. Open the repres_all database and be sure that there are three records corresponding to solid angle levels 1.5%, 8.5% and 19.5%.
4. Run ADS with the Classification flag checked and determine the topological type for each representation.

Exercise: Build the representations of the α-SrSi₂ structure considering different levels of interatomic distances (use the Distance and Solid Angle mode in the Representation Parameters window). Are there any differences with the previous method?

Answer: Solid angle level 19.5% belong to srs nets, the topology types of other nets do not contained in your databases. Distance mode generate four levels. Distance = 2.40 Å gives net srs topology, distances 3.30 A, 3.40 A, 3.85 A give nets with new topology.

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