The simulation of the vibrational properties of crystalline compounds.

R. Dovesi¹ and Yves Noel²

¹Dipartimento di Chimica IFM, Università di Torino.

²Universitè P. et M. Curie, Lab. PMMP, UMR 7160

E-mail: roberto.dovesi@unito.it

The vibrational properties of crystalline compounds can be simulated with the CRYSTAL06 computer code [1]; symmetry classification of the modes is performed automatically; many tools are available for the interpretation of the modes, including isotopic substitution and animation.

Garnets (pyrope [2], grossular and andradite [3], general formula X₃Y₂Si₃O₁₂, 80 atoms cell, cubic), katoite [4] (Ca₃Al₂[OH]₁₂ , 116 atoms in the cell) and olivines (forsterite [5] Mg₂SiO₄, 28 atoms in the unit cell) are used as examples to illustrate the capabilities of the code.

CRYSTAL is an ab initio program, that adopts a local variational basis set (“Atomic Orbitals”) to build the crystalline orbitals. An all-electron basis and the B3LYP hamiltonian have been used.

The 17 IR and 25 RAMAN active modes of garnets, and 35 (IR) and 36 (RAMAN) of forsterite are compared with available experimental data [6], [7]. The agreement is excellent in most of the cases (6-8 cm^–1 the mean absolute difference). In the few cases where large differences are observed, the origin of the discrepancy is discussed. Animation of modes for the systems indicated above can be found at www.crystal.unito.it/prtfreq/jmol.html.

[1] Saunders, V.R.; Dovesi, R.; Roetti, C.; Orlando, R.; Zicovich-Wilson, C.; Harison, N.H.; Doll, K.; Civalleri, B.; Bush, I.J..; D’Arco, Ph.; Llunell, M. (2003) CRYSTAL2003 user’s manual. University of Torino, Torino. [2] Pascale, F.; Zicovich-Wilson, C.; Orlando, R.; Dovesi, R. J. Phys. Chem., 2005, 109, 6146-6152. [3] Pascale, F.; Catti, M.; Damin, A.; Orlando, R.; Saunders, V.R.; Dovesi, R. J. Phys. Chem., 2005, 109, 18522-18527. [4] Orlando, R.; Torres, F.J.; Pascale, F.; Ugliengo, P.; Zicovich-Wilson, C.; Dovesi, R. J. Phys. Chem., 2006, 110, 692-701. [5] Noel, Y.; Catti, M.; D’Arco, Ph.; Dovesi, R. Phys Chem. Mineral. in press. [6] Kolesov, B.; Geiger, C. Phys. Chem. Min, 2000, 27, 645. [7] Hofmeister, A.; Chopelas, A. Phys. Chem. Min, 1991, 17, 503.