-) How are comments denoted "#" or "#!" ? Lines beginning with # are comment lines Lines beginning with #! are also comment lines, but some programs will read information from these lines PROGRAM SO1ION and CFIELD -) are programs cfield and so1ion different ? no, these programs do exactly the same job (as stand alone programs). However, if used as a module in mcphas, mcdisp etc the orientation of the crystal field coordinate system xyz with respect to the crystal axes abc is different: for MODULE=so1ion it is xyz||abc, whereas for MODULE=cfield it is xyz||cab PROGRAM MCDISP -) I get the error message: "Error 1: Chreduce: matrix B is not positiv definite" for some Q-vectors, what is going wrong ? most probably the magnetic structure you are using in mcdisp.mf is not the thermodynamically stable one. Try to rerun mcphas with less restrictions on the test structures and try to find a structure with a lower free energy. Probably the propagation vector of the stable magnetic structure is near to the Q-vector, where mcdisp gave the error. EXTERNAL MODULE IC1ION -) I cannot find ic1ion.mag after running ic1ion - what is the reason ? Please be aware that on some windows systems the file extension ".mag" is associated with other programs than mcphase and the explorer does not explicitely show the ".mag", the file is there, you can make sure by listing the directory contents with the command "dir" -) The programs mcphas/mcdisp/chrgplt/charges/singleion will not load the ic1ion.so module !? check if the first line in your single ion input file (.sipf) points to the path where the ic1ion.so module can be found: e.g. #!MODULE=c:\mcphas3_0\bin\ic1ion_module\ic1ion.so -) do I have to enter the free ion parameters F2 F4 F6 and XI in the sipf file ? No, usually it is sufficient to give the IONTYPE, e.g. IONTYPE=Co3+ and then the program automatically looks up F2 F4 F6 and XI in an internal table. However, if you are not happy with the values from the table, you can explicitely enter these constants. However for some ions these parameters are not available in standard tables, then you have to enter them. Please always check ic1ion.out to see if output is correct.