Exemple #1
0
 def cosets(self):
     """decomposing group of a bilayer with respect to the pair
     stabilizer. Coset representatives generate pairs, symmetry
     equivalent to self. Returns list of cosets of the decomposition"""
     if self._cosets:
         return self._cosets
     self._cosets = core.cosets_mod(self.stab, self.bilayer.stab, 1)
     return self._cosets
Exemple #2
0
    def fragments(self, fragments):
        nr_frags = len(fragments)
        assert nr_frags >= 0
        "The layer contains no fragments!"#fragments is non-empty
        
        if nr_frags == 1:
            item_fragments = []
            basic_fragment = fragments[0]
            order_basic = len(basic_fragment.stab) 
            order_self = len(self.stab)
            #basic checks that can be switched off
            #1a in __init__
            assert order_self % order_basic == 0,\
                "Order of Fragment.stab does not divide that of Layer.stab!"
            #1b ...
            assert all([item in self.stab for item in basic_fragment.stab]),\
                "There are symops in Fragment.stab that are not in Layer.stab!"


            lcosets = core.cosets_mod(basic_fragment.stab, self.stab)
            for lcoset in lcosets:
                item_fragments.append(Fragment.leftmult(basic_fragment, 
                                                                lcoset[0]))
            self._fragments = item_fragments
            #basic checks to do after coset decomposition
            #1c
            assert all([core.coset_in_stab((coset, self.stab)) \
                    for coset in lcosets]),\
                """Cosets of the consituent fragments
                        do not belong to the stabilizer of the layer!"""
            #1d
            assert all([core.divides((coset, self.stab)) for coset in lcosets]),\
                """Order of cosets of consituent fragments does not devides
                        order of the layers's stabilizer"""
        else:
            self._fragments = fragments
        #basic checks that can be switched off    
        coset_list = [fragment.coset for fragment in self._fragments]
        stab_list = [fragment.stab for fragment in self._fragments]
        #1e
        assert core.cosets_are_disjoint(coset_list), "Cosets are not disjoint!"
        #1f
        assert all([core.divides((stab, self.stab)) for stab in stab_list]),\
                """Order of stabilizer of some constituent fragments
                        does not devide order of the layers's stabilizer"""
        #1g
        assert all([core.coset_in_stab((stab, self.stab)) \
                    for stab in stab_list]),\
                """Stabilizers of the consituent fragments