Anharmonic, temperature, and matrix effects on the molecular structure and vibrational frequencies of lanthanide trihalides LnX3 (Ln = La, Lu; X = F, Cl)
| Autor: | Giuseppe Lanza, Camilla Minichino |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2005 |
| Předmět: |
Lanthanide
Trigonal planar molecular geometry MP2 and CCSD(T) Chemistry Anharmonic vibrations Anharmonicity Infrared spectroscopy Matrix Effects Molecular physics Bond length Molecular geometry Ab initio quantum chemistry methods Polarizability Computational chemistry Physics::Atomic and Molecular Clusters Physics::Chemical Physics Physical and Theoretical Chemistry |
| Popis: | MP2 and CCSD(T) ab initio calculations have been carried out to elucidate geometrical structure and vibrational frequencies of representative lanthanide trihalides LnX(3) (Ln = La, Lu; X = F, Cl) explicitly including temperature, anharmonic, inert-gas matrix, and spin-orbit effects. The results have been compared with gas-phase electron diffraction, gas-phase IR measurements, and IR spectra of molecules trapped in inert-gas matrices. On the Born-Oppenheimer surface LaCl(3), LuF(3), and LuCl(3) adopt trigonal planar (D(3)(h)()) geometry while LaF(3) assumes a slightly pyramidal (C(3)(v)()) structure. Because of normal-mode anharmonicities, the resulting thermal average bond angles are considerably lower than the equilibrium ones, while vibrationally averaged bond lengths are predicted to be longer. The inert-gas matrix effects, modeled by the coordination of two inert-gas molecules LnX(3).IG(2) (IG = Ne, Ar, Xe, and N(2)), are substantial and strongly depend on the polarizability of coordinating particles. Coordinating inert-gas units always favor the tendency of LnX(3) molecules to adopt planar structure and induce noticeable frequency shifts. |
| Databáze: | OpenAIRE |
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