The program mcphas (-calculation of the magnetic phase diagram) requires a single ion property input file of the same format as given above in section 6.2 (also for each ion in the crystallographic unit cell):
It follows a simple example (for more complicated examples see section 7.1.6 and mcphas.cf1 in the directory examples/ndcu2b_new):
#!MODULE=so1ion #<!--mcphas.cf--> # comment followed by # the ion type and the crystal field parameters [meV] IONTYPE=Nd3+ # - note you can also do any pure spin problem by entering e.g. IONTYPE=S=2.5 B20= 0.116765 B22 = 0.134172 B40 = 0.0019225 B42 = 0.0008704 B44 = 0.0016916 B60 = 0.0000476 B62 = 0.0000116 B64 = 0.0000421 B66 = 0.0003662
The reason for this unique choice is to make it possible to treat quadrupolar interactions - the generalisation of bilinear interactions to these higher order interactions is much easier in a unique axes convention.
Information for experienced users: the first line in the single ion property file can either refer to one of the standard single ion property modules (e.g. Kramers ground state doublet #!MODULE=kramers, full crystal field #!MODULE=so1ion) or a shared library file, which will be loaded dynamically into the program at runtime - for a description of this file see section 7.1.6.