Quantum chemical study of structure, vibrational spectra and thermodynamic properties of molecular and ionic clusters existing in vapours over strontium dichloride

Abstract

The cluster ions ${\text{SrCl}}_3^{-},$ $\text{S}{\text{r}}_2{\text{Cl}}_3^{+},$ $\text{S}{\text{r}}_3{\text{Cl}}_5^{+},$ $\text{S}{\text{r}}_4{\text{Cl}}_7^{+}$ and $\text{S}{\text{r}}_5{\text{Cl}}_9^{+}$ that were detected earlier in vapour over strontium dichloride at high temperatures ranging from 1100 to 1500 K have been studied theoretically. The equilibrium geometrical properties, vibrational spectra and thermodynamic properties were investigated by using the DFT, MP2 and MP4 methods. From the alternative structures considered, it was observed that the ions ${\text{SrCl}}_3^{-}$, $\text{S}{\text{r}}_2{\text{Cl}}_3^{+}$, $\text{S}{\text{r}}_3{\text{Cl}}_5^{+}$ and $\text{S}{\text{r}}_5{\text{Cl}}_9^{+}$ correspond to D_3h symmetry and $\text{S}{\text{r}}_4{\text{Cl}}_7^{+}$ corresponds to C_2v configuration, no isomers were identified for all cluster ions from the considered alternative structures. The enthalpies of formation, ${\mathrm{\Delta }}_{\text{f}}{H}^{\text{o}}$(0) of the cluster ions were determined (in kJ mol^–1): $-994\pm 3$ (${\text{SrCl}}_3^{-}$), $-410\pm 12$ ($\text{S}{\text{r}}_2{\text{Cl}}_3^{+}$), $-1202\pm 16$ ($\text{S}{\text{r}}_3{\text{Cl}}_5^{+}$), $-1962\pm 27$ and $-2718\pm 20$.

GRAPHICAL ABSTRACT

KEYWORDS:

• DFT
• MP2
• MP4
• geometrical properties
• thermodynamic properties

Acknowledgements

The authors are grateful to Prof. Alexander M. Pogrebnoi and his team members for their effort to detect the cluster ions existing in vapours over parent crystalline solid substances by using high-temperature mass spectrometer. This important information served as the baseline for this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).