ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The [FHCl]− molecular anion has been investigated in detail by means of state-of-the-art ab initio electronic structure methods, including restricted Hartree–Fock (RHF), Møller–Plesset perturbation theory (MP2–MP4), and coupled-cluster and Brueckner methods incorporating various degrees of excitation [CCSD, CCSD(T), BD, BD(T), and BD(TQ)]. The one-particle Gaussian basis sets ranged in quality from F[6s4p2d], Cl[10s7p2d], and H[4s2p] to F[18s13p6d4f], Cl[20s14p7d5f], and H[8s3p2d1f]. The first phase of the investigation focused on the prediction of thermochemical, spectroscopic, and bonding properties of [FHCl]− and the chemical interpretation thereof.The final proposals for the geometric structure and binding energy of the complex are re(H–F)=0.963±0.003 A(ring), Re(H–Cl)=1.925±0.015 A(ring), and D0(HF+Cl−)=21.8±0.4 kcal mol−1. A Morokuma decomposition of the ion-molecule bonding gave the following electrostatic (ES), polarization (PL), exchange repulsion (EX), dispersion (DISP), and charge-transfer plus higher-order mixing (CT+MIX) components of the vibrationless complexation energy: −27.3 (ES), −5.2 (PL), +18.3 (EX), −4.5 (DISP), and −5.0 (CT+MIX) kcal mol−1. The second phase of the work involved the construction of a CCSD global surface from 208 and 228 energy points for linear and bent conformations, respectively, these being fit to rms errors of only 3.9 and 9.3 cm−1, respectively, below 8000 cm−1. The surface was represented by a flexible analytic form which reproduces the quartic force field at equilibrium, exhibits the proper asymptotic properties, and is generally applicable to ion-molecule systems. The final phase of the study entailed the determination of converged J=0 and J=1 variational eigenstates of the [FHCl]− surface to near the HF+Cl− dissociation threshold by employing Jacobi coordinates and vibrational configuration interaction expansions in terms of natural modals.The fundamental vibrational frequencies given by the analysis were ν1=247, ν2=876, and ν3=2884 cm−1. The complete vibrational eigenspectrum was then analyzed in terms of several contemporary dynamical issues, including vibrational adiabaticity, anharmonic resonances, densities of high-lying states, and signatures of quantum ergodicity.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.466133
