Create a table of maximum flaw size a(delta T,P)

The model of Vance et al. (2007) involves determining the flaw size in a mineral grain, a, at which the stress intensity is maximum (this is what will open a crack). To save on computation time, a table was built that gives a for various temperature anisotropies (deltaT) and pressures (P). crack.sce simply looks up the table for the right a at the closest deltaT and P possible. The table is saved in the aTP.dat file, but can be rebuilt using aTable.sce.