You need two persons from your team for the success of a critical project. They don't like each other and not interested to work together. What do you do?

First, you should convince each of them alone to work in the specified job.

Second, you should promise them to give them a good gift (e.g. money) on the end of each successful stage.

Third, you should worn them that any fail caused by any problem they initiate may hurt them as well.

It's really difficult to obtain more that two heros of any team. For critical project if we need two of them, then there is no choice. We need to bring two team members together.

Looking for some work around?

You don't. If they have personal issues, it is their problem, and you are bringing it on a company level. Don't do that, because you are wasting company's resources. Their results will suffer and will be worse comparing to results they make by working on their own. To find that out, you will spend (loose) time and perhaps money. Find two members of your team which can work together instead, even if one of them is not that good as the one you wanted at first. You don't have time (and nerves) to waste.