Electronic polarizabilities, potential functions, and spectroscopic constants for diatomic molecules of alkali halides and alkali hydrides

Kumar, Munish; Shanker, J.

doi:10.1063/1.462714

Cited by 27 publications

(35 citation statements)

References 55 publications

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“…3,10,11 But the original approach of Pauling to calculate ionic R is based on the second-order Stark effect on H-like systems where the many-body effects are not included explicitly. 14 It is now realized that correlation must be included.…”

mentioning

confidence: 99%

Polarizability of an Ion in a Molecule. Applications of Rittner's Model to Alkali Halides and Hydrides Revisited

Hati

Datta

1996

J. Phys. Chem.

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An attempt is made to estimate the polarizability of an ion in an ionic diatomic molecule. The method is applied to alkali halide and hydride diatoms. In this connection, the applicability of Rittner's model to these test molecules is examined critically. A new phenomenological form of the repulsive part of Rittner's model is suggested. It is argued that the polarizability of an ion can be used as an index of the gas-phase chemical hardness of an ion in a molecule.Determination of the static electric dipole polarizability (hereinafter referred to simply as polarizability) R of an ion in a molecule is an old and important problem. It was realized long ago that R of an ion in a molecule is not the same as that in the free state. In 1934 Fajans 1 introduced a principle that states that R is diminished in the field of positive charge and increased in the field of negative charge. This statement was theoretically quantified later by Ruffa in 1963. 2 In the past there have been a number of attempts to estimate the R of an ion in a molecule. For a recent brief review on these efforts, see ref 3. Coker has found that in alkali halide crystals polarizability of an anion decreases while that of a cation increases. 4 Coker has also tried to find a relation between the R value of a free ion and that of the ion in a crystal. Here we are not interested in finding the R of an ion in a crystal lattice but that in an isolated molecule.A possible way of checking whether the R of an ion in a molecule has been estimated correctly is to work out Rittner's model 5 for a diatomic molecule AB in detail. In 1951, to explain bonding in specifically the alkali halide diatomics and to estimate their various spectroscopic constants theoretically, Rittner developed a model where an AB molecule is described as a cation-anion pair (polarizable charged spheres) held together by electrostatic attraction but prevented from collapse by a repulsive potential. In this model, the dipole moment µ and the ionic bond dissociation energy W are given by eqs 1 and 2, respectively. In eq 2 C is the van der Waals constant, φ(r) is the repulsive energy resulting from the overlap of the electron clouds of the two ions A + and B -, the last term represents the zero-point energy, and the superscripts + and -designate cation and anion, respectively. Using the derivatives of W with respect to r (of various orders) and some standard relations, 3,6 one can calculate the rotational-vibrational coupling constant (R e ), vibrational anharmonicity constant (ω e x e ), and other higher order spectroscopic constants, γ e and e (these notations are standard as used by Huber and Herzberg 7 ). This model, which because of its nature is likely to hold in rather ionic diatomics, has been examined by many workers in the past using mainly the alkali halide diatoms as the testing grounds 3,6,8-12 (in only one study 3 have the hydrides of the alkali metals been considered). As a general result, a simplification of Rittner's model by omitting the product terms R + R -, which arise ...

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mentioning

confidence: 99%

Polarizability of an Ion in a Molecule. Applications of Rittner's Model to Alkali Halides and Hydrides Revisited

Hati

Datta

1996

J. Phys. Chem.

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“…There has been considerable interest in the spectroscopic properties of monohalides such LiBr [1], BBr [2] and HBr [3] in the past several decades. A great amount of experimental and theoretical work has been done to obtain their spectroscopic parameters and molecular constants.…”

Section: Introductionmentioning

confidence: 99%

Theoretical studies on 14 Λ-S and 30 Ω states of BeBr molecule: potential energy curves, spectroscopic parameters and spin–orbit couplings

et al. 2013

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Using the complete active space self-consistent field (CASSCF) method followed by the internally contracted multi-reference configuration interaction (MRCI) approach in combination with the correlation-consistent basis sets, this paper studies the potential energy curves of X -S states of BeBr molecule and the corresponding 30 states for the first time. All the -S states correlate to the first two dissociation channels, Be( 1 S g ) + Br( 2 P u ) and Be( 3 P u ) + Br( 2 P u ), of BeBr molecule. Of these -S states, the 3 2 and 2 4 are found to be repulsive without the spin-orbit coupling, whereas 1 4 , 2 4 , 3 2 and 2 4 + are found to be repulsive with the spin-orbit coupling included. A 2 and 2 2 + possess the double well whether the spin-orbit coupling effect is included or not. Only 1 4 + , 1 4 − , 1 2 and 2 2 are found to be the inverted -S states. The spin-orbit coupling is accounted for by the state interaction approach with Breit-Pauli Hamiltonian using the all-electron cc-pCVTZ basis set. The potential energy curves determined by the internally contracted MRCI method are corrected for size-extensivity errors by means of the Davidson correction. Core-valence correlation correction is calculated with a cc-pCVTZ basis set. Scalar relativistic correction is included using the third-order Douglas-Kroll Hamiltonian approximation at the level of cc-pVTZ basis set. The spectroscopic parameters of all the -S and bound states are evaluated. The spectroscopic parameters are compared with those reported in the literature. Fair agreement is found between the present results and available measurements. In particular, the energy splitting of 204.43 cm −1 in the A 2 -S state agrees well with the measurements of 201 cm −1 . Analyses demonstrate that the spectroscopic parameters reported here can be expected to be reliably predicted ones.

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“…For evaluating ion in crystal polarizabilities it was thus suggested that w f be replaced by a potential dependent function. Shanker et al 3,4 extended this approach in an effort to estimate molecular state polarizabilities ␣ A or ␣ B for cation (A ϩ ) and anion (B Ϫ ) in a (A ϩ -B Ϫ ) diatomic molecule. The respective polarizabilities were represented by the expressions…”

Section: Introductionmentioning

confidence: 99%

“…This idea has subsequently been applied by a number of workers in calculating polarizabilities in studies of both crystalline 2,5 and molecular 4,6 states. A brief review of this approach may be found in the 1992 paper by Kumar and Shanker.…”

Section: Introductionmentioning

confidence: 99%

“…A brief review of this approach may be found in the 1992 paper by Kumar and Shanker. 4 A brief investigation of the validity of this approach in light of the law of conservation of energy suggests that it is mathematically unsound to define or view the polarizability as a potential dependent quantity as was suggested by the relations above.…”

Section: Introductionmentioning

confidence: 99%

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Comment on “A potential dependent polarizability?” [J. Chem. Phys. 96, 5289 (1992)]

Donald

Mulder

Szentpály

2000

The Journal of Chemical Physics

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Electronic polarizabilities, potential functions, and spectroscopic constants for diatomic molecules of alkali halides and alkali hydrides

Cited by 27 publications

References 55 publications

Polarizability of an Ion in a Molecule. Applications of Rittner's Model to Alkali Halides and Hydrides Revisited

Polarizability of an Ion in a Molecule. Applications of Rittner's Model to Alkali Halides and Hydrides Revisited

Theoretical studies on 14 Λ-S and 30 Ω states of BeBr molecule: potential energy curves, spectroscopic parameters and spin–orbit couplings

Comment on “A potential dependent polarizability?” [J. Chem. Phys. 96, 5289 (1992)]

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