- The brittle-ductile transition (BDT) is a very general phenomenon in materials science. The temperature TBDT in numerous materials correlates somewhat with the higher melting temperature Tm. We have earlier proposed the disclination (or rotation-dislocation) as a universal ingredient in the BDT. The present study is exclusively concerned with graphite, where Tm ≈ 4000 K. Our conclusion is that the energetics of 5- and 7-membered rings play a crucial role in determining these temperatures. However, experiment is to be invoked, should TBDT eventually be measured for graphite, so as to decide between various mechanisms, all of which here depend on 5- and 7-membered rings. One mechanism involves interlayer van der Waals coupling, whence a pressure experiment may hold the key.