How would you write mean energy? I came up with two different ways:

  • $\displaystyle\langle G_{\textrm{f}}^\circ(j) \rangle$ with the MathJax code \langle G_{\textrm{f}}^\circ(j) \rangle

  • $\displaystyle\overline{G}_{\textrm{f}}^\circ(j)$ with the MathJax code \overline{G}_{\textrm{f}}^\circ(j)

  • Or maybe another way?

I am looking for the proper use of this notation in the scientific literature.

  • $\begingroup$ When in doubt, simply indicate what you mean in text. $\endgroup$ – Zhe Oct 11 '17 at 13:09
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    $\begingroup$ To the question itself: I believe that the bar notation is most common for point values, while the bracket notation is mainly for functions. In any case I would write $\displaystyle \overline{G_{\textrm{f}}^\circ(j)}$. $\endgroup$ – Martin - マーチン Oct 11 '17 at 13:35
  • $\begingroup$ Depends on the convention used. Different people use different conventions but both indicate a mean. $\endgroup$ – logical x 2 Oct 15 '17 at 13:54
  • $\begingroup$ I would use \overline for representing arithmetic mean, and \langle \rangle for expected value (notice that their difference is commonly overlooked in chemistry literature). However, the proper use only requires stating the meaning in text. $\endgroup$ – user1420303 Jun 27 '18 at 15:37

Both the IUPAC 2008 Green Book (section 4.2) as well as the ACS Style Guide (specifically Chapter 11) agree that both methods of representing the mean value are acceptable. There might be some style guides / international standards that state otherwise, but for the average chemist these two are generally sufficient.

If ever in doubt, just state the meaning in text.

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    $\begingroup$ The international standard ISO 80000-2 Quantities and units – Part 2: Mathematical signs and symbols to be used in the natural sciences and technology agrees. $\endgroup$ – Loong Dec 31 '17 at 21:25
  • $\begingroup$ Good to know, too. I was lazy to check, hence the disclaimer. $\endgroup$ – orthocresol Dec 31 '17 at 21:53

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