Conversion of element density to TwinCAT-compatible constants.
Derived from periodictable
Per the public domain Python library periodictable:
Data were taken mostly from [#Lide1999]. These values are reproduced in [#ILL]. .. [#Lide1999] Lide. D. R., Ed., CRC Handbook of Chemistry and Physics, 80th ed. (CRC Press, Boca Raton, Florida, 1999) .. [#ILL] The ILL Neutron Data Booklet, Second Edition.