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Using first-principles calculations, we have studied the band-gap modulation as function of applied strain in black phosphorene (BP). Dynamical stability has been assessed as well. Three cases have been considered, in the first and second, the strain was applied uniaxially, in the x- and y-axis, separately. In the third, an isotropic in-plane strain was analyzed. Different strain percentages have been considered, ranging from 4% to 20%. The evolution of the band-gap is studied by using standard DFT and the G0W0 approach. The band-gap increases for small strains but then decreases for higher strains. A change in electronic behavior also takes place: the strained systems change from direct to indirect band-gap semiconductor, which is explained in terms of the s and p-orbitals overlap. Our study shows that BP is a system with a broad range of applications: in band-gap engineering, or as part of van der Waals heterostructures with materials of larger lattice parameters. Its stability, and direct band-gap behavior are not affected for less than 16% of uniaxial and biaxial strain. Our findings show that phosphorene could be deposited in a large number of substrates without losing its semiconductor behavior.

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A magneto-structural phase transition is investigated in single crystal CrN thin films grown by rf plasma molecular beam epitaxy on MgO(001) substrates. While still within the vacuum environment following MBE growth, in-situ low-temperature scanning tunneling microscopy, and in-situ variable low-temperature reflection high energy electron diffraction are applied, revealing an atomically smooth and metallic CrN (001) we also discuss results from first-principles theoretical calculations which explore various possible magneto-structural models.