  For holographic memory applications, the photorefraction of well-known
ferroelectric such as lithium niobate doped with different transition metals is
very important. First principles study assumes special significance in this
context, as to why certain transition metal atoms are better than the other. In
this work, Nb atom in LiNbO3 was substituted with transition elements having
valency greater than/equal to +5 for UV photorefraction applications, and
atomistic first-principles calculations were done using HSE06 functionals. The
d-states of the transitional elements were found to decrease the band-gap of
the host material having implications for a suitable material design. Minimum
band-gap was obtained for W, while Ta showed a maximum value. Absorption
coefficients were estimated for each material and based on their low values at
351 nm (i.e. for holographic applications) that is the usual UV photorefraction
wavelength, the elements found suitable were V, W, Ta, Mo. Then birefringence
properties for these crystals were also studied to predict that V and W were
good candidates.
