WordPress.org

Scott Taylor

Atom Publishing Protocol support for WordPress is still supported in this plugin. 
Support for Atom was dropped in WordPress core in version 3.5.

Atom Publishing Protocol

Atom Publishing Protocol support for WordPress

wokamoto

This plugin modifies RSS feeds and ATOM feeds as you want.
<h4>How to use</h4>
Putting the following templates into the current theme folder, then you can use the customized feed templates instead of the default ones.
<ul>
<li>feed-atom.php – Atom Feed Template for displaying Atom Posts feed.</li>
<li>feed-atom-comments.php – Atom Feed Template for displaying Atom Comments feed.</li>
<li>feed-rdf.php – RSS 1 RDF Feed Template for displaying RSS 1 Posts feed.</li>
<li>feed-rss.php – RSS 0.92 Feed Template for displaying RSS 0.92 Posts feed.</li>
<li>feed-rss2.php – RSS2 Feed Template for displaying RSS2 Posts feed.</li>
<li>feed-rss2-comments.php – RSS2 Feed Template for displaying RSS2 Comments feed.</li>
</ul>
Note: 
When these feed templates are not in the current theme folder, WordPress’s default feed templates will be used.

Feed Template Customize

This plugin modifies RSS feeds and ATOM feeds as you want.

Atom Publishing Protocol vs Feed Template Customize