Table 1 Elastic constants and bulk modulus in the Voigt-Reuss-Hill (VRH) approximation [as this is appropriate for polycrystalline samples (36)] of the most stable polymorphs calculated with the LDA (9) and RPA (2226) methods.

LDA results are very close to those from RPA, showing the suitability of LDA for estimating second energy derivatives. Results are in units of gigapascal.

C11C22C33C12C23C13BVRH
c-BNLDA997997997101101101402
c-BNRPA968968968818181378
h-BN(AA′)LDA9239262817433138
h-BN(AA′)RPA91091529153−4−5131
m-BNLDA7518394515610068160
m-BNRPA745830431379058151