CCL:G: Scientific notation in Gaussian 16



Hi Andrew,

In Fortran (I'm a Fortran programmer), we use "D" to designate a double-precision representation written in scientific notation, while "E" designates simple precision. That is very likely the reason for the "D" since a quick glance at the Wikipedia page for the list of Quantum Chemistry and Solid-State Physics software shows that Gaussian is written in Fortran.

Best regards,

Marcos
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Dr. Marcos Verissimo Alves
Prof. Adjunto II, Curso de Física Computacional
Instituto de Ciências Exatas
Universidade Federal Fluminense
Volta Redonda - RJ, Brasil



Em ter., 11 de jan. de 2022 às 16:33, Andrew DeYoung andrewdaviddeyoung###gmail.com <owner-chemistry(-)ccl.net> escreveu:
Hi,

It appears that various quantities that are output by Gaussian 16 use notation of the form 6.626D-34.  Is it correct for me to assume that this represents 6.626*10^(-34), and is equivalent to the scientific notation 6.626E-34 or 6.626e-34 used in other areas, such as in C/C++, Python, and MATLAB?  Or does the "D" represent anything different from, or in addition to, "*10^"?

Thank you for bearing with me with this question.  (I am what we call in the US a millennial, and am not terribly well acquainted with the sometimes historical origins and meanings of notation!)

Best,
Andrew

Andrew DeYoung, PhD
Department of Chemistry
Carnegie Mellon University