Breaking bonds with the left eigenstate completely renormalized coupled-cluster method

Abstract

The recently developed [P. Piecuch and M. Wloch, J. Chem. Phys.123, 224105 (2005)] size-extensive left eigenstate completely renormalized (CR) coupled-cluster (CC) singles (S), doubles (D), and noniterative triples (T) approach, termed CR-CC(2,3) and abbreviated in this paper as CCL, is compared with the full configuration interaction (FCI) method for all possible types of single bond-breaking reactions between C, H, Si, and Cl (except H2) and the H2SiSiH2 double bond-breaking reaction. The CCL method is in excellent agreement with FCI in the entire region R=1-3Re for all of the studied single bond-breaking reactions, whereR and Re are the bond distance and the equilibrium bond length, respectively. The CCL method recovers the FCI results to within approximately 1mhartree in the region R=1-3Reof the H-SiH3, H-Cl, H3Si-SiH3, Cl-CH3, H-CH3, and H3C-SiH3bonds. The maximum errors are −2.1, 1.6, and 1.6mhartree in the R=1-3Re region of the H3C-CH3, Cl-Cl, and H3Si-Clbonds, respectively, while the discrepancy for the H2SiSiH2 double bond-breaking reaction is 6.6 (8.5)mhartree at R=2(3)Re. CCL also predicts more accurate relative energies than the conventional CCSD and CCSD(T) approaches, and the predecessor of CR-CC(2,3) termed CR-CCSD(T). Keywords Chemical bonds, Hydrogen reactions, Hydrogen bonding, Nuclear reaction models, Chemical vapor deposition Disciplines Chemistry CommentsThe following article appeared in Journal of Chemical Physics 127 (2007) The recently developed ͓P. Piecuch and M. Wloch, J. Chem. Phys. 123, 224105 ͑2005͔͒ size-extensive left eigenstate completely renormalized ͑CR͒ coupled-cluster ͑CC͒ singles ͑S͒, doubles ͑D͒, and noniterative triples ͑T͒ approach, termed CR-CC͑2,3͒ and abbreviated in this paper as CCL, is compared with the full configuration interaction ͑FCI͒ method for all possible types of single bond-breaking reactions between C, H, Si, and Cl ͑except H 2 ͒ and the H 2 Siv SiH 2 double bond-breaking reaction. The CCL method is in excellent agreement with FCI in the entire region R =1-3R e for all of the studied single bond-breaking reactions, where R and R e are the bond distance and the equilibrium bond length, respectively. The CCL method recovers the FCI results to within approximately 1 mhartree in the region R =1-3R e of the H -SiH 3 , H-Cl, H 3 Si-SiH 3 , Cl-CH 3 , H-CH 3 , and H 3 C -SiH 3 bonds. The maximum errors are −2.1, 1.6, and 1.6 mhartree in the R =1-3R e region of the H 3 C-CH 3 , Cl-Cl, and H 3 Si-Cl bonds, respectively, while the discrepancy for the H 2 Siv SiH 2 double bond-breaking reaction is 6.6 ͑8.5͒ mhartree at R =2͑3͒R e . CCL also predicts more accurate relative energies than the conventional CCSD and CCSD͑T͒ approaches, and the predecessor of CR-CC͑2,3͒ termed CR-CCSD͑T͒.

Stereoelectronic Effects on Molecular Geometries and State-Energy Splittings of Ligated Monocopper Dioxygen Complexes

“…Prior work on molecules containing Cu 2 O 2 2+ cores has demonstrated that the CR-CC(2,3) level can predict accurate relative energies for isomers differing significantly in their degree of biradical character. 50,51 Several other benchmark studies and applications have shown that in spite of its single-reference character, the CR-CC(2,3) approach is capable of providing a highly accurate description of the lowest-energy singlet and triplet states of biradicals and systems undergoing significant bond rearrangements, [84][85][86][87][88][89][90][91][92] where the conventional CC methods, such as CCSD and CCSD(T), 93 fail or have considerable problems. On the basis of this positive experience, we regard the CR-CC(2,3) level as a reference level for assessing the accuracy of other methods used in the present study.…”

Breaking Bonds of Open-Shell Species with the Restricted Open-Shell Size Extensive Left Eigenstate Completely Renormalized Coupled-Cluster Method

“…31 The CCL method belongs to a larger CR-CC(m, n) family based on the biorthogonal formulation 29,30 of the method of moments coupled-cluster equations. [32][33][34][35] CCL has been shown to reproduce full configuration interaction (FCI) PESs with small errors for the single-bond-breaking reactions of nine closed-shell C-H-Si-Cl molecules.…”

“…[32][33][34][35] CCL has been shown to reproduce full configuration interaction (FCI) PESs with small errors for the single-bond-breaking reactions of nine closed-shell C-H-Si-Cl molecules. [29][30][31] The restricted open-shell CCL (ROCCL) method has been shown to properly break the OH and F 2 + bonds within reasonable accuracy. 28 The nonparallelity errors (NPE, defined 28 as the difference between the most positive and most negative signed errors along a given a The MRCI(Q) numbers are not available for H2Si-Cl due to CASSCF convergence problems in the R(Si-Cl) ) 3.4-6.8 Å region.…”

“…3 , each of which has one less H atom than the closed shell molecules studied previously. 31 The accuracy of the ROCCL PESs is compared with that of the conventional UCCSD(T) 36 method. The ROCCL potential energy error curves are also compared with the MRMP2 ones.…”

Composite Method Employing Pseudopotential at CCSD(T) Level

“…This approach is abbreviated as CR-CCL and is appropriately described by Piecuch(Piecuch et al, 2002) and Ge (Ge et al, 2007). …”