Any clematis can be used as a groundcover. Generally speaking, clematis do better if they are climbing over something as they can be prone to being eaten by earwigs and other nasties that like living under them. Might not be an issue with the hot humid climates that you garden in.

You might also want to consider Jouinana praecox as a ground cover. I have it growing on the ground and through a tree shaped variegated ligustrum and it has not seemed to be bothered by the usual bugs that like to chomp on clematis leaves and flowers. Sure isn't as invasive either. The stems will root if the area they are in is mulched and there is some ground moisture.

My pictures don't do just to the flowers and their color so have linked you to its listing on the Brushwood Nursery site for it below my pictures.

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Here is a link that might be useful: Brushwood Nursery Listing