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,


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 <owner-chemistry(-)> escreveu:

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!)


Andrew DeYoung, PhD
Department of Chemistry
Carnegie Mellon University