  In this work, different computational methods such as HF, B3LYP, range
separated functionals (CAM-B3LYP and LC-BLYP) with 6-31G* basis set were
applied to investigate the electronic, spectroscopic and nonlinear optical
properties of L-threoninium picrate (LTHP) molecule for the first time. The
calculated values of IR and Raman vibrational frequencies were found to be in a
good agreement with the experimental results. Time dependent density functional
theory has been applied to calculate the electronic and photophysical
properties such as excitation energy, dipole moment and frontier molecular
orbital (FMO) energies of LTHP molecule. The excitation energy value calculated
by CAM-B3LYP is found to be at 351 nm which is in close agreement with the
experimental values. The total/partial DOS (T/PDOS) was determined using
GGA/BLYP. The total dipole moment ({\mu}tot), static total and anisotropy of
polarizability ({\alpha}tot, {\Delta}{\alpha}) and static first
hyperpolarizability (\b{eta}0, \b{eta}tot) values were calculated and compared
with the reference compound. The {\mu}tot and \b{eta}tot are found to be 3 and
51 time higher than urea molecule respectively. The FMOs, molecular
electrostatic potential (MEP), global reactivity descriptors were also
calculated and discussed. All these results suggest that the L-threoninium
picrate would be a good candidate for optoelectronic device applications.
