Benchmark ab initio thermochemistry of the isomers of diimide, N2H2, using accurate computed structures and anharmonic force fields

Martin, Jan M. L.

doi:10.1080/002689799165530

Cited by 8 publications

(6 citation statements)

References 51 publications

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“…The accuracy of such an approach was tested by comparison with the heat of formation of trans -N 2 H 2 . The results show that relative, zero-point-energy-corrected, MRCI(+Q)/aug-cc-pVQZ energies agree to chemical accuracy with the best experimental and theoretical results. By further scaling the ab initio dynamical correlation energy of the N 2 H 2 system, after the Davidson corrections were put in, not only the good relative positions for the minima and saddle points were maintained but also the correct exothermicities insured for all dissociation channels .…”

Section: Ammonia Gas-phase Chemistrymentioning

confidence: 56%

“…We emphasize that the single-valued DMBE form for N 2 H 2 and its fragments includes a proper description of long-range forces at all asymptotic channels. Moreover, the geometry and spectroscopy of the main stationary points are reproduced accurately when compared with the best available theoretical − and experimental , data. In fact, the above DMBE potential energy surfaces 63-65,76 probably stand as the most accurate representations published thus far, being commended for both quantum , and classical dynamics studies of the associated reactions.…”

Section: Ammonia Gas-phase Chemistrymentioning

confidence: 80%

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Predicting Catalysis: Understanding Ammonia Synthesis from First-Principles Calculations

et al. 2006

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Here, we give a full account of a large collaborative effort toward an atomic-scale understanding of modern industrial ammonia production over ruthenium catalysts. We show that overall rates of ammonia production can be determined by applying various levels of theory (including transition state theory with or without tunneling corrections, and quantum dynamics) to a range of relevant elementary reaction steps, such as N 2 dissociation, H 2 dissociation, and hydrogenation of the intermediate reactants. A complete kinetic model based on the most relevant elementary steps can be established for any given point along an industrial reactor, and the kinetic results can be integrated over the catalyst bed to determine the industrial reactor yield. We find that, given the present uncertainties, the rate of ammonia production is well-determined directly from our atomic-scale calculations. Furthermore, our studies provide new insight into several related fields, for instance, gas-phase and electrochemical ammonia synthesis. The success of predicting the outcome of a catalytic reaction from first-principles calculations supports our point of view that, in the future, theory will be a fully integrated tool in the search for the next generation of catalysts.

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Section: Ammonia Gas-phase Chemistrymentioning

confidence: 56%

Section: Ammonia Gas-phase Chemistrymentioning

confidence: 80%

Predicting Catalysis: Understanding Ammonia Synthesis from First-Principles Calculations

et al. 2006

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“…Specifically, the cc-pVDZ and cc-pVTZ basis set were utilized, whose schemes are [3s2p1d/2s1p] and [4s3p2d1f/3s2p1d] for the [C/H] atoms. There is a general agreement in the fact that for computing DFT molecular relative energies, a basis set of spdf quality is usually sufficient to get the asymptotic regime . Of course, the same is not true for ab initio methods without assistance of extrapolation techniques .…”

Section: Methodsmentioning

confidence: 99%

Description of C(sp²)−C(sp²) Rotation in Butadiene by Density Functionals

2001

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The torsional potential of 1,3-butadiene has been calculated using several ab initio methodologies. For each value of the CdC-CdC torsional angle, the fully relaxed geometry and energy have been determined using the Hartree-Fock (HF) method, Mo ¨eller-Plesset perturbation theory up to the second order (MP2), and the coupled-cluster method with single, doubles, and parethentical triples (CCSD(T)), as well as using several exchange-correlation combinations of functionals in density functional theory (DFT) calculations. From the results obtained, the achievements and drawbacks of current density functionals in the description of torsional profiles have been rationalized, and some possible breakthroughs have been proposed to improve their performance.

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“…The IVO-CASCI method is one portion of the latest generation of effective valence shell Hamiltonian computer codes that have been interfaced to the GAMESS program. 33 The CASSCF data are obtained using the DALTON package. 34 Table I clearly reflect the well-known fact that the optimized geometrical parameters depend on the method and on the basis set used.…”

Section: A N 2 Hmentioning

confidence: 99%

Potential energy curve for isomerization of N2H2 and C2H4 using the improved virtual orbital multireference Møller–Plesset perturbation theory

Chaudhuri

Freed

Chattopadhyay

et al. 2008

The Journal of Chemical Physics

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Multireference Møller-Plesset (MRMP) perturbation theory [K. Hirao, Chem. Phys. Lett. 190, 374 (1992)] is modified to use improved virtual orbitals (IVOs) and is applied to study ground state potential energy curves for isomerization and dissociation of the N2H2 and C2H4 molecules. In contrast to traditional MRMP or multistate multiconfiguration quasidegenerate perturbation theory where the reference functions are obtained from (often difficult to converge) state averaged multiconfiguration self-consistent field methods, our reference functions are represented in terms of computationally efficient IVOs. For convenience in comparisons with other methods, a first order complete active space configuration interaction (CASCI) calculation with the IVOs is followed by the use of the IVOs in MRMP to incorporate residual electron correlation effects. The potential energy curves calculated from the IVO-MRMP method are compared with computations using state-of-the-art coupled cluster singles and doubles (CCSD) methods and variants thereof to assess the efficacy of the IVO-MRMP scheme. The present study clearly demonstrates that unlike the CCSD and its variants, the IVO-MRMP approach provides smooth and reliable ground state potential energy curves for isomerization of these systems. Although the rigorously size-extensive completely renormalized CC theory with noniterative triples corrections (CR-CC(2,3)) likewise provides relatively smooth curves, the CR-CC(2,3) calculations overestimate the cis-trans barrier height for N2H2. The ground state spectroscopic constants predicted by the IVO-CASCI method agree well with experiment and with other highly correlated ab initio methods.

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Benchmark ab initio thermochemistry of the isomers of diimide, N2H2, using accurate computed structures and anharmonic force fields

Cited by 8 publications

References 51 publications

Predicting Catalysis: Understanding Ammonia Synthesis from First-Principles Calculations

Predicting Catalysis: Understanding Ammonia Synthesis from First-Principles Calculations

Description of C(sp²)−C(sp²) Rotation in Butadiene by Density Functionals

Potential energy curve for isomerization of N2H2 and C2H4 using the improved virtual orbital multireference Møller–Plesset perturbation theory

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Benchmark ab initio thermochemistry of the isomers of diimide, N2H2, using accurate computed structures and anharmonic force fields

Cited by 8 publications

References 51 publications

Predicting Catalysis: Understanding Ammonia Synthesis from First-Principles Calculations

Predicting Catalysis: Understanding Ammonia Synthesis from First-Principles Calculations

Description of C(sp2)−C(sp2) Rotation in Butadiene by Density Functionals

Potential energy curve for isomerization of N2H2 and C2H4 using the improved virtual orbital multireference Møller–Plesset perturbation theory

Contact Info

Product

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Description of C(sp²)−C(sp²) Rotation in Butadiene by Density Functionals