This data block contains the nuclear electric quadrupole moment of each atomic species. It has the following format:
%BLOCK SPECIES_Q [units] CCC1/I1 R1 CCC2/I2 R2 . . . %ENDBLOCK SPECIES_Q
The first entry on a line is the symbol or atomic number of the species. This must correspond with the species symbol or atomic number of the species in the POSITIONS_FRAC or POSITIONS_ABS block. The second entry on each line is the quadrupole moment of that species.
Not all of the species present in the system have to appear in the SPECIES_Q block. Any that are not present will be assigned the default quadrupole moment for that species. However, if the symbol specified for a species is not a standard symbol in the periodic table, the quadrupole moment of the species must be specified.
The units entry specifies the units in which the quadrupole moment is defined. If no units are given, the default unit of atomic quadrupole moment, Barn, is used. The only other supported unit is fm2, i.e., femtometer2.
%BLOCK SPECIES_Q Barn B 0.0405900000 N 0.0201000000 %ENDBLOCK SPECIES_Q
CASTEP keyword glossary
CASTEP cell keywords and data blocks