Elemental Smiting( Complete Divine, p. 81)
You can channel elemental energy to deal extra damage to creatures tied to a specifi c element.
Ability to turn creatures with an elemental subtype,
Once per round, you can spend a turn attempt as a free action when making a melee attack. If you successfully strike a creature that you could turn with that turn attempt because of its elemental subtype, you may add a bonus on your damage roll equal to your cleric level. If your attack misses, the turn attempt is lost to no effect. For example, a cleric with the Fire domain could use this feat to smite a water elemental or any other creature with the water subtype (since he would normally turn creatures with the water subtype with his domain power).
You may only activate this feat by spending a turn attempt that would normally be used to turn creatures with a specifi c elemental subtype (air, earth, fi re, or water). Unlike other divine feats, you can't use a turn or rebuke undead attempt (or other turning attempt) to activate the feat.