These ebuilds come from http://overlays.gentoo.org/proj/sunrise.
If you have some problems, go to the official site first.
hoomd : HOOMD performs general purpose molecular dynamics simulations on NVIDIA GPUs ( http://codeblue.umich.edu/hoomd-blue/index.html )
Add an ebuild in portage :
The ebuild is now in the portage tree.
You can also use layman : emerge layman then layman -a sunrise
For Paludis use this rsync : rsync://gentoo.zugaina.org/sunrise-portage
If you have a problem : ycarus(-at-)zugaina.org