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Comparison of theoretical methods for the determination of the Li + Affinities of neutral and anionic first‐ and second‐row bases
Author(s) -
Bene Janet E. Del,
Shavitt Isaiah
Publication year - 1990
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560382436
Subject(s) - chemistry , affinities , basis set , perturbation theory (quantum mechanics) , computational chemistry , deprotonation , coupled cluster , ion , møller–plesset perturbation theory , lithium (medication) , density functional theory , molecule , stereochemistry , physics , quantum mechanics , medicine , organic chemistry , endocrinology
The structures of the Li + complexes with the bases NH 3 , H 2 O, HF, PH 3 , H 2 S, HCl, and HCN and with the corresponding deprotonated anions have been optimized using second‐order Møller–Plesset perturbation theory with the 6‐31+G(d,p) basis set. Single‐point calculations on all species were performed using the 6‐31+G(2d,2p) basis set using the following correlation methods: many‐body (Møller–Plesset) perturbation theory at second ( MP 2), third ( MP 3), and fourth ( MP 4) order; the linearized coupled‐cluster method ( LCCM ); the averaged coupled pair functional ( ACPF ); configuration interaction with all single and double excitations ( CISD ); and CISD with the Davidson and Pople corrections. The computed lithium ion affinities of the neutral bases vary between 15 and 40 kcal/mol, while the values for the anionic bases are between 145 and 190 kcal/mol. The effect of correlation on the lithium ion affinities varies between about –5 and +2 kcal/mol. For each neutral base, the lithium ion affinities computed with the various correlated methods agree with each other to between 0.1 and 1 kcal/mol. For the anions, the various correlated methods agree with each other to between 0.5 and 3 kcal/mol. Agreement with the available experimental data is within the estimated uncertainties in the latter. Structural differences between corresponding first‐ and second‐row complexes reflect differences in the strength of the electrostatic interaction due to differences in the charge distribution.