Using CMU Serif Upright Italic instead of chemgreek?

Question

I recently moved over to luaLaTeX from pdfLaTeX which means I am no longer quite so font-constrained. I found this answer which shows how to load this alphabet of upright Greek letters instead of the math alphabet. I don't want to load them in place of the math alphabet, I want that to stay italic. I want to use them for commands like \chemalpha to replace the commands from the chemgreek package. Alternatively, making chemgreek use this alphabet would work, though I can manually write each command if need be.

I made this example, but it doesn't actually work, it replaces the wrong alphabet and the \newcommand{\chemalpha}{α} don't actually DO anything as it has no idea what α is.

\documentclass{article}
\usepackage[math-style=upright]{unicode-math}
\setmathfont{Latin Modern Math}
\setmathfont[range=up/{Latin,latin,Greek,greek}]{CMU Serif Upright Italic}
\usepackage{cfr-lm}
\newcommand{\chemalpha}{α}
\newcommand{\chembeta}{β}
\newcommand{\chemeta}{η}
\newcommand{\chemkappa}{κ}
\begin{document}
( \alpha + \beta = \pi )
([^{\text{n}}\text{Bu}_4 \text{N}]_2 [(\text{UO}_2 )_2 (µη^{2}:η^{2}O_2 )(NO_3 )_2 (µ\text{Au(CN)}_2 )_2 ])
\chemalpha
\chembeta
\chemeta
\chemkappa
\end{document}

Answer 1

Glad you found my older answer helpful. First, a MWE:

\documentclass{article}
\tracinglostchars=2
\usepackage{newcomputermodern}
% Alternatively, \setmathrm{CMU Serif} to load an upright font that contains Greek.
\newcommand\chem[1]{\mathrm{#1}}
\newcommand\chemalpha{\chem\mupalpha} % \chem α would work too.
\newcommand\chembeta{\chem\mupbeta}
\newcommand\chemeta{\chem\mupeta}
\newcommand\chemkappa{\chem\mupkappa}
\begin{document}
( \alpha + \beta = \pi )
([^{\chem{n}}\chem{Bu}_4 \chem{N}]_2 \bigl[(\chem{UO}_2 )_2
   (\chem{µη}^{2}:\chem{η}^{2}\chem{O}_2 )(\chem{NO}_3 )_2
   \bigl( \chem{µ}\chem{Au}(\chem{CN})_2 \bigr)_2 \bigr])
( \chemalpha
   \chembeta
   \chemeta
   \chemkappa
)
αβηκ
\mupalpha\mupbeta\mupeta\mupkappa
\end{document}

Chemists traditionally don’t use upright italic style for chemical formulas, but if you did want to, you’d write \symup{\alpha} in math mode to use the letters you set with \setmathfont[range=up]. To use the upright italic style in text mode, you would probably set up the {ui} shape similarly to the interface of cfr-lm.

What you probably want to do here is to set your \mathrm font to one that has Greek letters, such as New Computer Modern or CMU Serif. The default font, Latin Modern, doesn’t, and that’s why it wasn’t working for you. I introduce a command \chem so you can tweak it or switch to another font (with something like \textnormal{\chemfont #1}, or by declaring a new math font face) by changing that one line.

I took a few liberties with the source. You don’t want to use \text here, since it makes the formatting of the surrounding text bleed through, and therefore might give you CN. If you need to use a main font that does not contain Greek, you can \setmathrm{NewComputerModern}.

I changed the formatting slightly, to make nested outer parentheses slightly bigger than inner parentheses, and the brackets around those the same size.

You also would only want to load cfr-lm if you are compiling in PDFTeX.

You do, however, want to set \tracinglostchars=2. This will give you a warning if you try to use a character that the current font does not have, which is the bug you were getting with \chemalpha, etc. By default, the warning will be silently buried in the middle of your .log file.

Answer 2

Based on the comment by cgnieder

\usepackage{newcomputermodern}\usepackage{chemgreek}\selectchemgreekmapping{fontspec}

is very simple and works with my existing setup almost perfectly.