A systematic theoretical study of the harmonic vibrational frequencies for polyatomic molecules: The single, double, and perturbative triple excitation coupled-cluster [CCSD(T)] method

Abstract

Articles you may be interested inSymmetric and asymmetric triple excitation corrections for the orbital-optimized coupled-cluster doubles method: Improving upon CCSD(T) and CCSD(T)Λ: Preliminary application The method of moments of coupled-cluster equations and the renormalized CCSD[T], CCSD(T), CCSD(TQ), and CCSDT(Q) approachesA systematic theoretical study of harmonic vibrational frequencies: The single and double excitation coupled cluster (CCSD) method Analytic gradient methods have been used to predict the harmonic vibrational frequencies and the infrared (IR) intensities of HCN, HNC, CO 2 , CH 4 , NHt, C 2 H 2 , H 2 0, H 2 CO, and NH3 at the single, double, and perturbative triple excitation coupled-cluster [CCSD(T)] level of theory. All studies were performed using a double zeta plus polarization (DZ+P) basis set with a contraction scheme of (9s5pld/4s2pld) for C, N, and ° and (4s1p/2s1p) for H.

An ab initio study on the ground state HBO–BOH system

“…Given any basis set the correlated levels of theory predict longer bond lengths than those with the SCF method, as is usually the case. [37][38][39][40] It is interesting to note that an increase of the basis set size is accompanied by increase of the BH bond lengths and decrease of the BO bond lengths. At the highest level of theory, TZ2P( f ,d) CCSD͑T͒, the agreement between theory and experiment is very good as expected, 40 the differences being only 0.0013 Å ͑BH͒ and 0.0060 Å ͑BO͒, respectively.…”

Ab Initio Investigation of the Ground Potential Energy Surface of the CO2+·Ar Ion

“…Spectroscopic constants and minimum total energy calculated for CO 2 + using the various basis sets and electron correlation methods are reported in Table 2. Recent calculations on 10 closed-shell polyatomic molecules 31,32 and three openshell diatomic molecules 33 have established some trends relating the effect of increases in basis set size and/or electron correlation on calculated bond lengths and harmonic frequencies which can be compared to the present results. The calculated value of r e for CO 2 + is found to decrease with increased zeta level of the basis set, increase with increased electron correlation, and increase with basis set augmentation.…”

Coupled-cluster vibrational frequencies for open, ring and superoxide sulfur dioxide

“…1) by employing the TZ2P(f ) CCSD and TZ2P(f ) CCSD(T) methods. The investigations of Thomas et al [13] indicate that TZ2P(f ) CCSD and TZ2P(f ) CCSD(T) provide predicted harmonic frequencies which reproduce experimentally deduced harmonic frequencies with an average error of 1.5% and 0.6%, respectively, for a group of relatively well behaved systems. Although such accuracy is not likely for SO 2 , which exhibits more multi-reference character than those systems studied by Thomas et al TZ2P(f ) CCSD and CCSD(T) should still provide predictions which are superior to TZ2P( f ) CISD predictions, since coupledcluster methods are generally less sensitive to the quality of the reference function than are CI techniques.…”