Turkish Airlines Miles&Smiles - Redeposit fee for only taking one leg of RT itinerary?

I am planning an itinerary on Turkish where I need to travel between two cities one way. However, the one way fare is significantly higher than the roundtrip fare.

Can I buy the roundtrip fare and just not take the return portion without any penalties? I'd like to get credited miles for the portion of the itinerary I do fly, so, is there some redeposit fee that I'll get charged for the miles from the return portion that I'm not planning to take?

Thanks!

Try using THY.com for the domestic flights.

On the domestic market, there is no return fare. All fares are one-way.