1. The HCl/H2O Solid System: Infrared Spectra of HCl Tri-and Hexahydrate
Víctor J. Herrero1. R. Escribano1, D. Fernández-Torre1, B. Maté1, M. A. Moreno1 and I. K. Ortega1,2
1) Instituto de Estructura de la Materia, CSIC, Madrid, Spain
2) Departamento de Química Física y Analítica, Universidad de Jaén, Spain

2. HCl hydrates Phase diagram X Ray Crystal Structures Trihydrate:
H5O2+Cl- H2O
Hexahydrate:
H9O4+Cl- 2(H2O)

3. Theoretical method: SIESTA
“Spanish Initiative for Electronic Simulations with Thousands of Atoms”
Quantum mechanical DFT calculations for periodic systems (solids)
Characteristics: linear combination of atomic orbitals, localized atomic wavefunctions; real-space grid; running time and memory scale linearly with number of atoms
Details: DZP; localized orbitals within 100 meV; grid size Ry
Calculations of equilibrium structures, binding energy and prediction of IR spectrum ( frequencies and intensities of normal modes)

4. HCl·3H2O Optimized Structure
Zundel ion
H5O2+

5. Calculated spectrum of HCl·3H2O
Width 50 cm -1
Width H2O5+
cm -1
RAIR this work
Transmision (Devlin)

6. HCl·3H2O.

7. 3297 cm-1

8. HCl·3H2O.

9. 2944 cm-1

10. HCl·6H2O Optimized structure
Eigen ion: H9O4+

11. HCl·6H2O: Calculated spectrum
Width 50 cm -1
Width H9O4+
cm -1
RAIR this work
Transmision (Devlin)

12. HCl·6H2O
cm-1

13. 2494 cm-1

14. HCl·6H2O
cm-1

15. 2213 cm-1

16. HCl·6H2O
cm-1

17. 1606 cm-1

18. Future work
Consideration of bandwidths in the theoretical calculations
Further studies of hydrated protons in crystals
Sample orientation effects