  We study theoretically the structural and electronic response of layered bulk
black phosphorus to in-layer strain. Ab initio density functional theory (DFT)
calculations reveal that the strain energy and interlayer spacing display a
strong anisotropy with respect to the uniaxial strain direction. To correctly
describe the dependence of the fundamental band gap on strain, we used the
computationally more involved GW quasiparticle approach that is free of
parameters and superior to DFT studies, which are known to underestimate gap
energies. We find that the band gap depends sensitively on the in-layer strain
and even vanishes at compressive strain values exceeding about 2%, thus
suggesting a possible application of black P in strain-controlled infrared
devices.
