Version4.1_Notes.txt

Notes on changes for MatMCNP Version 4.1
 - July 2020
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(1) The mass defects for each isotope were updated to reflect the values found here:
    
    https://www.nndc.bnl.gov/nudat2/indx_sigma.jsp 
    
    At the time of the update this tool stated this “Nuclear Wallet Cards database version of 7/10/2019.”

(2) The value used to calculate the atomic masses (931.494 MeV/amu) was parameterized. As originally written
    K. Kajder used the number in ~100 places in the code. Now, that value is a declared parameter in the 
    "NWC_DATABASE" module. This was done because this value is likely to change (see comments in the source),
    but it's value was NOT changed in this version. For all practical purposes, the difference between this value
    and the official value will not be detectable in MatMCNP. However, should one wish to update mass defects in 
    the future based on a different definition of the MeV/amu than the one used in 2004, it is easily 
    accomplished with a one line change.

(3) The default cross section set was updated to reflect the ENDF/B-VIII.0 release at 293.6 K (*.00c). For most
    elements and isotopes, the only change was as simple as change "13027.80c" to "13027.00c". However, the new
    cross section evaluation provided new evaluations for O-18 (treated as O-16 in previous versions), Neon 
    (not treated by MatMCNP previously), Ytterbium (not treated by MatMCNP previously), and Osmium (not treated 
    by MatMCNP previously). In addition, both Carbon and Platinum are now treated isotopically instead of as 
    elements. These changes made the "naturalzaid" routine obsolete and required changes to the "print_data"
    routine.

(4) The code was modified to accept command line arguments for the input and output files. Now the code has 2 usages:

    >> MatMCNP.exe

    - The default "matmcnp.inp" and "matmcnp.out" files will be used. This method will continue to be used by the 
      batch (csh) and perl scripts.

    >> MatMCNP.exe  input-filename  output-filename

    - This is the updated code and requires 2 arguments. The filenames should be less than 80 characters.