Toward a less costly but accurate calculation of the CCSD(T)/CBS noncovalent interaction energy

The popular method of calculating the noncovalent interaction energies at the coupled-cluster single-, double-, and perturbative triple-excitations [CCSD(T)] theory level in the complete basis set (CBS) limit was to add a CCSD(T) correction term to the CBS second-order Møller-Plesset perturbation theory (MP2). The CCSD(T) correction term is the difference between the CCSD(T) and MP2 interaction energies evaluated in a medium basis set. However, the CCSD(T) calculations with the medium basis sets are still very expensive for systems with more than 30 atoms. Comparatively, the domain-based local pair natural orbital coupled-cluster method [DLPNO-CCSD(T)] can be applied to large systems with over 1,000 atoms. Considering both the computational accuracy and efficiency, in this work, we propose a new scheme to calculate the CCSD(T)/CBS interaction energies. In this scheme, the MP2/CBS term keeps intact and the CCSD(T) correction term is replaced by a DLPNO-CCSD(T) correction term which is the difference between the DLPNO-CCSD(T) and DLPNO-MP2 interaction energies evaluated in a medium basis set. The interaction energies of the noncovalent systems in the S22, HSG, HBC6, NBC10, and S66 databases were recalculated employing this new scheme. The consistent and tight settings of the truncation parameters for DLPNO-CCSD(T) and DLPNO-MP2 in this noncanonical CCSD(T)/CBS calculations lead to the maximum absolute deviation and root-mean-square deviation from the canonical CCSD(T)/CBS interaction energies of less than or equal to 0.28 kcal/mol and 0.09 kcal/mol, respectively. The high accuracy and low cost of this new computational scheme make it an excellent candidate for the study of large noncovalent systems.     

Generalized Prediction of Enthalpies of Formation Using DLPNO-CCSD(T) Ab Initio Calculations for Molecules Containing the Elements H,C, N,O, F,S, Cl,Br

The prediction of thermochemical properties such as enthalpies of formation is of crucial importance, both in research and industrial applications, especially for systems involving not well-characterized molecules, such as biomass systems (bio-oils), or systems involving new compounds (new-generation refrigerants). It is highly desirable to obtain an efficient method by which these values can be predicted. Ab initio-based calculations can be very accurate for predicting gas phase thermochemical properties and are usually more versatile than group contribution methods. In this work, we propose a general extension of the work of Paulechka and Kazakov, using very accurate and efficient domain-based local pair natural orbital-coupled cluster theory ab initio calculations, to determine the enthalpies of formation of a broad variety of molecules. New sets of regressed atomic contributions are proposed for a larger group of elements: H, C, N, O, F, S, Cl, and Br. Excellent predictions are obtained for the most studied compounds (bio-oil compounds and refrigerants). © 2019 Wiley Periodicals, Inc.     

DFT,DLPNO-CCSD(T), and NEVPT2 benchmark study of the reaction between ferrocenium and trimethylphosphine

The reaction between ferrocenium and trimethylphosphine was studied using density functional theory (DFT), domain-based local pair natural orbital coupled cluster theory with single-, double-, and perturbative triple excitations (DLPNO-CCSD(T)), and N-electron valence state perturbation theory (NEVPT2). The accuracy of the DFT functionals decreases compared to the DLPNO-CCSD(T) level in the following order: M06-L > TPSS > M06, BLYP > PBE, PBE0, B3LYP > > PWPB95 > > DSD-BLYP. The roles of thermochemical, continuum solvation (SMD), and counterpoise corrections were evaluated. Grimme's D3 empirical dispersion correction is essential for all functionals studied except M06 and M06-L. The reliability of the frequency calculations performed directly within the SMD was confirmed. The systems showed no significant multireference character according to T₁ and T₂ diagnostics and the fractional occupation number (FOD) weighted electron density analysis. The multireference NEVPT2 calculations gave qualitatively valid conclusions about the reaction mechanism. However, a multireference approach is generally not recommended because it requires arbitrary chosen active spaces.     

Accurate prediction of enthalpies of formation for a large set of organic compounds

This article describes a multiparameter calibration model, which improves the accuracy of density functional theory (DFT) for the prediction of standard enthalpies of formation for a large set of organic compounds. The model applies atom based, bond based, electronic, and radical environmental correction terms to calibrate the calculated enthalpies of formation at B3LYP/6‐31G(d,p) level by a least‐square method. A diverse data set of 771 closed‐shell compounds and radicals is used to train the model. The leave‐one‐out cross validation squared correlation coefficient q² of 0.84 and squared correlation coefficient r² of 0.86 for the final model are obtained. The meanabsolute error in enthalpies of formation for the dataset is reduced from 4.9 kcal/mol before calibration to 2.1 kcal/mol after calibration. Five‐fold cross validation is also used to estimate the performance of the calibration model and similar results are obtained. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Assessing the validity of DLPNO-CCSD(T) in the calculation of activation and reaction energies of ubiquitous enzymatic reactions

The domain-based local pair natural orbital coupled-cluster with single, double, and perturbative triples excitation (DLPNO-CCSD(T)) method was employed to portray the activation and reaction energies of four ubiquitous enzymatic reactions, and its performance was confronted to CCSD(T)/complete basis set (CBS) to assess its accuracy and robustness in this specific field. The DLPNO-CCSD(T) results were also confronted to those of a set of density functionals (DFs) to understand the benefit of implementing this technique in enzymatic quantum mechanics/molecular mechanics (QM/MM) calculations as a second QM component, which is often treated with DF theory (DFT). On average, the DLPNO-CCSD(T)/aug-cc-pVTZ results were 0.51 kcal·mol⁻¹ apart from the canonic CCSD(T)/CBS, without noticeable biases toward any of the reactions under study. All DFs fell short to the DLPNO-CCSD(T), both in terms of accuracy and robustness, which suggests that this method is advantageous to characterize enzymatic reactions and that its use in QM/MM calculations, either alone or in conjugation with DFT, in a two-region QM layer (DLPNO-CCSD(T):DFT), should enhance the quality and faithfulness of the results.     

Accurate prediction of the enthalpies of formation for xanthophylls

This study investigates the applications of computational approaches in the prediction of enthalpies of formation (ΔH(f)) for C-, H-, and O-containing compounds. Molecular mechanics (MM4) molecular mechanics method, density functional theory (DFT) combined with the atomic equivalent (AE) and group equivalent (GE) schemes, and DFT-based correlation corrected atomization (CCAZ) were used. We emphasized on the application to xanthophylls, C-, H-, and O-containing carotenoids which consist of ～ 100 atoms and extended π-delocaization systems. Within the training set, MM4 predictions are more accurate than those obtained using AE and GE; however a systematic underestimation was observed in the extended systems. ΔH(f) for the training set molecules predicted by CCAZ combined with DFT are in very good agreement with the G3 results. The average absolute deviations (AADs) of CCAZ combined with B3LYP and MPWB1K are 0.38 and 0.53 kcal/mol compared with the G3 data, and are 0.74 and 0.69 kcal/mol compared with the available experimental data, respectively. Consistency of the CCAZ approach for the selected xanthophylls is revealed by the AAD of 2.68 kcal/mol between B3LYP-CCAZ and MPWB1K-CCAZ.     

Reduction of rhodium(III) trifluoroacetate by norbornadiene

It was shown that the action of heat on rhodium(III) trifluoroacetate with norbornadiene (NBD) leads to its reduction and the formation of red crystals of [Rh(CF₃COO)NBD]₂. The formation of the complex was confirmed by elemental analysis and IR, electronic, and x-ray photoelectron spectra. The reaction shows that Rh-Rh compounds can disproportionate under the influence of NBD with the formation of Rh(I) and Rh(III).Institute of Chemical Physics at Chernogolovka, Russian Academy of Sciences, 142432 Chernogolovka. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1438–1440, June, 1992.     

From CCSD(T)/aug-cc-pVTZ-J to CCSD(T) complete basis set limit isotropic nuclear magnetic shieldings via affordable DFT/CBS calculations

It is shown that a linear correlation exists between nuclear shielding constants for nine small inorganic and organic molecules (N(2), CO, CO(2), NH(3), CH(4), C(2)H(2), C(2)H(4), C(2)H(6) and C(6)H(6)) calculated with 47 methods (42 DFT methods, RHF, MP2, SOPPA, SOPPA(CCSD), CCSD(T)) and the aug-cc-pVTZ-J basis set and corresponding complete basis set results, estimated from calculations with the family of polarization-consistent pcS-n basis sets. This implies that the remaining basis set error of the aug-cc-pVTZ-J basis set is very similar in DFT and CCSD(T) calculations. As the aug-cc-pVTZ-J basis set is significantly smaller, CCSD(T)/aug-cc-pVTZ-J calculations allow in combination with affordable DFT/pcS-n complete basis set calculations the prediction of nuclear shieldings at the CCSD(T) level of nearly similar accuracy as those, obtained by fitting results obtained from computationally demanding pcS-n calculations at the CCSD(T) limit. A significant saving of computational efforts can thus be achieved by scaling inexpensive CCSD(T)/aug-cc-pVTZ-J calculations of nuclear isotropic shieldings with affordable DFT complete basis set limit corrections.     

Enhanced visible light photocatalytic activity of CeO2@Zn0.5Cd0.5S by facile Ce(IV)/Ce(III) cycle

In this study, CeO₂@Zn_0.5Cd_0.5S heterostructure (Ce@ZCS) is synthesized via a simple two-step hydrothermal method. The effect of CeO₂ loading on the visible-light photoactivity of Zn_0.5Cd_0.5S is mainly investigated. It is found that Ce@ZCS shows a 1.9 times activity as high as ZCS for the MB degradation. The improved activity mainly results from the significant enhanced charge separation by CeO₂, in which the electron transfer is obviously promoted by the facile Ce(IV)/Ce(III) cycle. The excited electrons of ZCS is easy to transfer to CeO₂, thus obviously increasing the charge separation of ZCS. The accepted electrons by CeO₂ may easily be captured by the adsorbed O₂ to form O₂⁻, and then O₂⁻ could combine with H⁺/H₂O to form HO₂, and OH. Finally, O₂⁻, h⁺ and OH are confirmed as the major oxidative species in photocatalytic reaction for Ce@ZCS, and a possible photocatalytic mechanism is proposed. The cheap, efficient Ce@ZCS photocatalyst could be applied for practical waste water treatment.     

Determinations of combustion and formation enthalpies of C_(60)and C_(70)

Ｆｕｌｌｅｒｅｎｅｓａｒｅａｋｉｎｄｏｆｃａｒｂｏｎａｌｌｏｔｒｏｐｅｓｆｏｕｎｄｒｅｃｅｎｔｌｙ,ａｎｄｈａｖｅｄｉｓｔｉｎｃｔｉｖｅｓｔｒｕｃｔｕｒｅｓａｎｄｐｒｏｐｅｒｔｉｅｓ.Ｆｏｒｅｘａｍｐｌｅ,Ｃ60ｈａｓａｆｏｏｔｂａｌｌｌｉｋｅｃａｒｂｏｎｓｋｅｌｅｔｏｎｗｉｔｈ20ｓｉｘｍｅｍｂｅｒｅｄｒｉｎｇｓ,12ｆｉｖｅｍｅｍｂｅｒｅｄｒｉｎｇｓａｎｄａｌａｒｇｅｂａｌｌｓｈｅｌｌｌｉｋｅπｂｏｎｄｓｙｓｔｅｍ.Ａｌｔｅｒｎａｔｉｖｅｌｙ,Ｃ70ｈａｓａｎｅｌｌｉｐｓｏｉｄｌｉｋｅｃａｒｂｏｎｓｋｅｌ…     

The enthalpies of formation and evolved gas detection

The standard molar enthalpies of formation of H₄SiW₁₂O₄₀·6H₂O (I), H₄SiW₁₂O₄₀·6DMF·H₂O (II), H₄SiW₁₂O₄₀·8DMSO·H₂O (III) have been determined. Thermodynamic cycles were designed, and the heat of reactions in the thermodynamic cycles were measured calorimetrically. The infrared spectra were compared with those of the heteropoly anion α-H₄SiW₁₂O₄₀ [1] and of the ligands DMF and DMSO. The evolved gas from the adducts was monitored by a quadrupole mass spectrometer at a heating rate of 16 deg·min^?1.     

Prediction of hydrocarbon enthalpies of formation by various thermochemical schemes

The correlation consistent composite approach (ccCA) has been used to compute the enthalpies of formation (ΔH_f′s) for 60 closed‐shell, neutral hydrocarbon molecules selected from an established set (Cioslowski et al., J. Chem. Phys. 2000 , 113, 9377). This set of thermodynamic values includes ΔH_f's for hydrocarbons that span a range of molecular sizes, degrees of aromaticity, and geometrical configurations, and, as such, provides a rigorous assessment of ccCA's applicability to a variety of hydrocarbons. The ΔH_f's were calculated via atomization energies, isodesmic reactions, and hypohomodesmotic reactions. In addition, for 12 of the aromatic molecules in the set that are larger than benzene, the energies of ring‐conserved isodesmic reactions were used to calculate the ΔH_f′s. Using an atomization energy approach to determine the ΔH_f′s, the lowest mean absolute deviation (MAD) from experiment achieved by ccCA for the 60 hydrocarbons was 1.10 kcal mol^?1. The use of the mixed Gaussian/inverse exponential complete basis set extrapolation scheme (ccCA‐P) in conjunction with hypohomodesmotic reaction energies resulted in a MAD of 0.87 kcal mol^?1. This value is compared with MADs of 1.17, 1.18, and 1.28 kcal mol^?1 obtained via the Gaussian‐4 (G4), Gaussian‐3 (G3), and Gaussian‐3(MP2) [G3(MP2)] methods, respectively (using the hypohomodesmotic reactions). © 2012 Wiley Periodicals, Inc.     

Predictions of solvation and vaporization enthalpies. 1.n-alkane +n-alkane solutions

A simple method for the calculation of the enthalpy of solvation is presented and demonstrated for 35 n-alkane + n-alkane solutions at 25°C. There is a good agreement between the predicted and experimental values. The calculation was based on the separation of the solvation enthalpy into the cavity formation and solute-solvent interaction contributions. The former term was determined from the activation enthalpy of the solvent viscous flow and solute molar volume while the latter on the basis of the dispersion energy using van der Waals diameters for n-propyl group. The procedure was also successful in prediction of the vaporization enthalpy of C₅–C₁₇ n-alkanes.     

Accurate prediction of heats of formation by a combined method of B3LYP and neural network correction

Recently, we proposed the X1 method which combines the B3LYP/6‐311+G(3df,2p)//B3LYP/6‐311+G(d,p) method with a neural network correction for an accurate yet efficient prediction of heats of formation (Wu and Xu, J Chem Phys 2007, 127, 214105). In this contribution, we discuss in detail how to set up the X1 neural network. We give examples, showing how to apply the X1 method and how the applicability of X1 can be extended. The overall mean absolute deviation of the X1 method from experiment for the 488 heats of formation is 1.52 kcal/mol compared with 9.44 kcal/mol for the original B3LYP results. © 2008 Wiley Periodicals, Inc. J Comput Chem 2009     

Gibbs energy of activation for thermal isomerization of (1Z)‐acetaldehyde hydrazone and (1Z)‐acetaldehyde N,N‐dimethylhydrazone by Gaussian‐4 theory and CCSD(T)/CBS computations

In this article, we examined the Gibbs energy of activation for the Z/E thermal isomerization reaction of (1Z)‐acetaldehyde hydrazone and (1Z)‐acetaldehyde N,N‐dimethylhydrazone, at 298.15 K in the solvent of cyclohexane. We carried out computations employing both the Gaussian‐4 (G4) theory and the coupled cluster method using both single and double substitutions and triple excitations noniteratively, CCSD(T). The CCSD(T) energy is extrapolated to the complete basis set (CBS). We compared the calculated results to the available experimental observation. It appeared that both G4 and CCSD(T)/CBS computations overestimated the experimental value by as much as about 6 and 12 kcal/mol in the present two cases. We discussed possible sources of error and proposed the experimental kinetic data could be questionable. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009     

The structure and thermochemistry of 3:4,5:6-dibenzo-2-hydroxymethylene-cyclohepta-3,5-dienenone (1) and some related compounds

Condensed and gas phase enthalpies of formation of 3:4,5:6-dibenzo-2-hydroxymethylene-cyclohepta-3,5-dienenone (1, (−199.1 ± 16.4), (−70.5 ± 20.5) kJ mol⁻¹, respectively) and 3,4,6,7-dibenzobicyclo[3.2.1]nona-3,6-dien-2-one (2, (−79.7 ± 22.9), (20.1 ± 23.1) kJ mol⁻¹) are reported. Sublimation enthalpies at T=298.15 K for these compounds were evaluated by combining the fusion enthalpies at T = 298.15 K (1, (12.5 ± 1.8); 2, (5.3 ± 1.7) kJ mol⁻¹) adjusted from DSC measurements at the melting temperature (1, (T _fus, 357.7 K, 16.9 ± 1.3 kJ mol⁻¹)); 2, (T _fus, 383.3 K, 10.9 ± 0.1) kJ mol⁻¹) with the vaporization enthalpies at T = 298.15 K (1, (116.1 ± 12.1); 2, (94.5 ± 2.2) kJ mol⁻¹) measured by correlation-gas chromatography. The vaporization enthalpies of benzoin ((98.5 ± 12.5) kJ mol⁻¹) and 7-heptadecanone ((94.5 ± 1.8) kJ mol⁻¹) at T = 298.15 K and the fusion enthalpy of phenyl salicylate (T _fus, 312.7 K, 18.4 ± 0.5) kJ mol⁻¹) were also determined for the correlations. The crystal structure of 1 was determined by X-ray crystallography. Compound 1 exists entirely in the enol form and resembles the crystal structure found for benzoylacetone.     

在Pd(Ⅱ)-Cu(Ⅱ)/活性炭催化剂上水汽对CO氧化的影响

研究了ＣＯ在Ｐｄ（ Ⅱ） － Ｃｕ（ Ⅱ）／ 活性炭催化剂上的催化氧化反应，发现当空气中含有水汽时催化活性大大提高。并对ＣＯ 络合催化机理进行了讨论，求得总包反应级数约为１ ．３，表观活化能为５０ ．４６ｋＪ·ｍｏｌ－ １ 。