Recently, i am performing the GW calulations for GaSe, i used Abinit to generate the KSS database. The first question is , during the calculations, i found the two datasets of Abinit (the first is groud-state calculation and the second is KSS generation) have the different k points (the parameter nkpt) with the same input of automatic k-points generater. is this situiation reasonable? i am wondering the reason for this results owing to the parameter symmorphi i used. If i am right, can anybody tell me more details why used this parameters. (
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the interpretition from Abinit tutorial is :With symmorphi=1, symmetry operations with a non-symmorphic vector are allowed. With symmorphi=0, they are not allowed. In the latter case, if the symmetry operations are specified in the input file, the code will stop and print an error message if a non-symmorphic vector is encountered. By contrast, if the symmetry operations are to be determined automatically (if nsym=0), then the set of symmetries will not include the non-symmorphic operations.
Note : this feature exist because in a previous status of the GW calculations, non-symmorphic symmetry operations could not be exploited. Thus, the k points were restricted to the IBZ. In order to prepare GW calculations, and to perform GW calculations, symmorphi=0 was to be used, together with nsym=0.) Since this dosnt have much senese to me, can you give me some more specific reference that explain why use this parameter.
Cheers!
Sheleon