I'm assuming you're picking up I-81 somewhere and taking the 81-77-85 route to Atlanta. That's the quickest way. And a pretty way as you go through the Blue Ridge Mountains of Virginia. However, I've never been on the portion of I-77 that you'll be on, so I cannot comment about the scenery.
You could take I-81 all the way to its conclusion at I-40 just south of Morristown, TN. I know that route, and that is a nice drive. From I-40, you can see the foothills of the Smokies, although you won't actually go into the Smokies.
Take I-40 west through Knoxville until you pick up I-75 south about 15 miles west of Knoxville. Be careful. For about 20 miles, I-40 and I-75 are the same road.
Take I-75 south through Chattanooga until you eventually hit Atlanta. If you want, you could visit Lookout Mountain, just west of Chattonooga
It adds about another 40 miles and 45 minutes to your ride. It may be shorter (or longer) depending on where your friends live in Atlanta. Good luck.