Using \AA for angstrom is not working for me. When I write 1 \AA all I get is 2 (r)A in the output. I have tried putting the curly brackets around it {\AA} but still no success. I do not know why. I have even tried changing the fonts I am using. Any help will be appreciated.

up vote 31 down vote accepted

\AA is a text command which essentially becomes \r{A}; \r is the command producing the "ring accent" and is invalid in math mode. Here's a way:

\newcommand{\angstrom}{\mbox{\normalfont\AA}}

If the unit must be used also in subscripts or superscripts,

\usepackage{amsmath} % or simply amstext
\newcommand{\angstrom}{\text{\normalfont\AA}}

Following daleif suggestion, a more compact version would be

\usepackage{amsmath} % or simply amstext
\newcommand{\angstrom}{\textup{\AA}}

(amsmath is necessary, otherwise \textup doesn't change sizes in subscripts).

However, the best practice when dealing with units is to use siunitx as suggested by quinmars. The macros \si and \SI made available by it provide the correct spacing.

I'd suggest to use the siunitx package. If you want a quantity, use:

The lattice constant $a = \SI{2.0}{\angstrom}$ is ...

if you only need the unit, use:

Atomic distances are measured in \si{\angstrom}.
  • 5
    And you can get the real ångström character with the lmodern package and \sisetup{text-angstrom={Å},math-angstrom={\text{Å}}} with UTF-8 input. – Andrey Vihrov Jul 28 '11 at 9:11

@egreg answer is correct but in the community is hard to convince others (reluctant-TeX) collaborators to use \mbox{\normalfont\AA} or \text{\normalfont\AA} to write Angstrom units. At best one can hope that they use \mathrm{\AA} (so Angstrom doesn't appear as italic in math formulas). They are just too used to write \AA.

What I suggest is this:

\usepackage{amsmath}
\let\oldAA\AA
\renewcommand{\AA}{\text{\normalfont\oldAA}}

What caused this problem for me is that I redefined the \r command. That is, I had a

\renewcommand{\r}

in my preamble. If this is the case, change the name of the command you called \r to something else.

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