For instance, there's something called the Nudged Elastic Band (NEB) method that can be bolted on to existing ab initio / quantum chemistry codes, that allows o

For instance, there's something called the Nudged Elastic Band (NEB) method that can be bolted on to existing ab initio / quantum chemistry codes, that allows one to calculate energy barriers between different states. Then you can blend those barriers in with some reaction rate theory that can give you some estimate of which potential reaction pathways could be useful and which not.