The energy required to form a twin in niobium was experimentally determined to be of the order of 109erg/cm3. This high energy was explained in terms of a continuous nucleation theory which also accounted for the observed morphology of twins in bcc transition metals and the heat evolved in the process.

Twinning in Niobium, a Continuous Nucleation Theory. B.J.Shaw: Metallurgical Transactions, 1973, 4[4], 1003-9