Figure 2: The calculated plots for (a) frequency vs phonon
dispersion curves (b) frequency vs density of states.
Infrared and Raman Spectroscopy
We have used Density Functional Perturbation theory [30] in order to
revealthe Infrared (IR) and Raman spectroscopy. IR and Raman modes of
vibrations obtained for the studied compound are displayed in table 2.
As shown in figures (3-4), modes at values of frequency 93.224
cm-1, 113.244 cm-1, 251.0
cm-1 and 436.144 cm-1 are observed
due to displacement of Li+and\({\ [\text{BH}_{4}]}^{-}\) ions. At the values of
frequency of 1054.1 cm-1 and 1305.3
cm-1, bending modes of vibration occurred due to H and
B atoms. The symmetrical modes of vibration have been observed at the
values of 2303.5 cm-1, 2387.5 cm-1and 2401.6 cm-1, whereas, antisymmetrical modes of
vibration were observed at frequencies of 2345.920
cm-1 and 2377.9 cm-1 due to motion
of H atoms. Our calculated Raman active and IR active modes are found to
be consistent with the available experimental studies [45]. The
calculated modes of vibrations are in close agreement with the earlier
theoretical studies with some slightly different modes [31]. The
possible reason may be the use of different calculation approaches and
the terms related to interactions and exchange potentials etc.
Table 2: Infrared and Raman spectroscopy of
LiBH4. Character of modes are represented as inactive
(i), Raman active (R), and infrared active (IR) and irreducible
representation (Irrep.).