How do I use a circle as a math accent (larger than \mathring)?

Question

To denote the interior of a set, I'd like to have a command \interior. Now, as one can learn from this post, one possibility is to use \mathring. This is a neat command, but it produces a circle that to my taste is too small for the purpose. Of course one can experiment with \overset{\circ}{...}, but this way I had difficulties getting satisfactory vertical and in particular horizontal positioning of the \circ. An example:

$\mathring{I}\ \mathring{J}\ \overset{\circ}{I}\ \overset{\circ}{J}$

yields .

If one has a close look then one sees that the \circ over the J should be moved to the right more than the \circ over the J! Is there a way to obtain the same nice automatic positioning as with mathring?

Answer 1

You can use \accentset from the accents package:

$ \mathring{I}\ \mathring{J}\ \accentset{\circ}{I}\ \accentset{\circ}{J} $

Answer 2

In the end I'm using an even larger circle than in Caramdir's great answer: accents sets the \circ in \scriptscriptstyle; I'm using \scriptstyle. To not affect the line spacing so much, I have the circle lowered and let it stick out a bit of the bounding box of the resulting accented character. (In print it looks nicer than on screen ...)

\documentclass{article}
\usepackage{amsmath,accents}
\newcommand{\interior}[1]{\accentset{\smash{\raisebox{-0.12ex}{$\scriptstyle\circ$}}}{#1}\rule{0pt}{2.3ex}}
\fboxrule0.0001pt \fboxsep0pt
\begin{document}
$\mathring{I}\ \accentset{\circ}{I}\ \interior{I}$ \fbox{$\interior{I}$}
\end{document}

Answer 3

There is also the Unicode combining character U+030A ◌̊ "COMBINING RING ABOVE":

https://en.wikipedia.org/wiki/Ring_(diacritic)#Overring