Can you buy an unlocked iPhone 5s in America and use it in Ireland?

I'm hoping to buy an unlocked iPhone and was wondering if I could buy one over in America and use it over in Ireland, I live in Ireland and would use it over here like a normal mobile phone!
Is this possible or will I run into difficulty over in Ireland? I'm with vodafone and hope to stay with them! I don't no much about (GSM OR IIRC) so try and explane a little easier.

The iphone 5s seems to have a lot of the 2G and 3G bands which are also used in Ireland, so I don't see why not. Presuming it really is unlocked, it should work with a Vodafone nanosim. However (presuming it ever does get here) LTE won't work because the phone'll use the American bands for that.