Ab initio calculation of vibrational frequencies and Raman spectra of barium peroxide glass including comparison of tetrahedral BaO4 with GeO4 and SiO4

We have calculated the vibrational frequencies of clusters of atoms from the first principles by using the density-functional theory in the local density approximation (LDA). We are also able to calculate the electronic binding energy for all of the clusters of atoms from the optimized structure. We have made clusters of BanOm (n, m = 1–6) and have determined the bond lengths, vibrational frequencies as well as intensities in each case. We find that the peroxide cluster BaO2 occurs with the O–O vibrational frequency of 836.3 cm−1. We also find that a glass network occurs in the material which explains the vibrational frequency of 67 cm−1. The calculated values agree with those measured from the Raman spectra of barium peroxide and Ba-B-oxide glass. We have calculated the vibrational frequencies of BaO4, GeO4 and SiO4 each in tetrahedral configuration and find that the vibrational frequencies in these systems depend on the inverse square root of the atomic mass.

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► New ab initio calculation of BaO. The atomic number of Ba is 56. Hence, the calculation is quite long and time consuming.
► Identification of Raman lines is very important. Some times there are impurities which can also create Raman lines. Hence identification of lines is required.
► The results lead to identification of lines and hence can be useful for extension to other atoms. Therefore, we have discovered a general method for the identification of molecules which are creating the Raman lines.
► The method is applicable to other molecules.
► In amorphous state other clusters of atoms are possible. Hence we can predict the clusters which are possibly present. We also provide a comparison of Ba with Ge and Si oxides.