Implementation of the modified Becke–Johnson meta-GGA functional in Quantum Espresso

In this paper we present an implementation of the modified Becke–Johnson meta-GGA functional (TB09) in the PWSCF program of Quantum ESPRESSO package via the Libxc library. Using the functionals of TB09 we calculated the band gaps of some semiconductors and compared the results with previous calculations and experiments. We showed that combining GGA pseudo-potential with TB09 functionals would improve greatly the band gaps compared with the GGA calculations. The details of our implementation and code samples are also given.