The molecular electric quadrupole moment and electric-field-gradient induced birefringence (Buckingham effect) of Cl₂

Issue title: Computational aspects of electric polarizability calculations: Atoms, Molecules and clusters, Part I

Article type: Research Article

Authors: Cappelli, Chiara^{a; **} | Ekström, Ulf^{a; ***} | Rizzo, Antonio^{a; *} | Coriani, Sonia^b

Affiliations: [a] Istituto per i Processi Chimico-Fisici del CNR, Area della Ricerca, via G. Moruzzi 1, I-56126 Pisa, Italy | [b] Dipartimento di Scienze Chimiche, Università degli Studi di Trieste, Via L. Giorgieri 1, I-34127 Trieste, Italy

Correspondence: [*] Corresponding author. Tel.: +39 050 315 2456; Fax: +39 050 315 2442; E-mail: [email protected].

Note: [**] Current affiliation: POLYLAB, INFN, Pisa.

Note: [***] Current affiliation: University of Linköping, Sweden.

Abstract: An ab initio investigation of the molecular properties rationalizing the electric-field-gradient induced birefringence (Buckingham effect) for Cl2 is presented. The quadrupole moment is determined using hierarchies of basis sets and wavefunction models. The electric dipole polarizability, the dipole – dipole – quadrupole and dipole – dipole – magnetic dipole hyperpolarizabilities are determined exploiting a Coupled Cluster Singles and Doubles (CCSD) response approach. The properties are zero-point vibrationally averaged, and the contribution of excited ro-vibrational states accounted for. To this end, the interatomic 1Σg+ ground state potential has been computed at CCSD plus perturbative triples – CCSD(T) – level employing a large augmented correlation consistent basis set. The effect of relativity is estimated at the Dirac-Hartree-Fock level. Our best value for the quadrupole moment of Cl2 is (2.327 ± 0.010) au and it is in excellent agreement with experiment which, after revision and dependent on the procedure employed for correcting the original estimate of (2.24 ± 0.04) au of Graham et al., [Mol. Phys., 93, 49, (1998)], ranges from (2.31 ± 0.04) au to (2.36 ± 0.04) au.

Keywords: molecular quadrupole moment, birefringence, electric field gradient, electric dipole (hyper)polarizabilities, coupled cluster theory, relativistic effects, molecular vibrations

DOI: 10.3233/JCM-2004-4313

Journal: Journal of Computational Methods in Sciences and Engineering, vol. 4, no. 3, pp. 365-380, 2004