Doubly contracted CI method

Wang, Yubin; Suo, Binbin; Zhai, Gaohong; Wen, Zhenhai

doi:10.1016/j.cplett.2004.03.092

Cited by 20 publications

(11 citation statements)

References 20 publications

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“…For the elementary reaction without a transition state, the MEP was developed using the relaxed potential energy surface scan with the CASSCF/6‐311G(d,p) method61–66 and the energies in the MEP path were refined with the multireference configuration interaction method MRCISD/6‐311G(d,p) (i.e., second‐order CI, SOCI, by involving all the symmetry adapted complete active space (CAS) configurations as the reference configurations) by using the GAMESS67 plus Xi'an CI68–72 programs. The CAS was chosen by (6,5) (i.e., six active electrons in five active orbitals) for closed shell and (5,5) for open shell systems in our calculations.…”

Section: Methodology and Modelsmentioning

confidence: 99%

Reaction rate of propene pyrolysis

Han

Liu

et al. 2011

J Comput Chem

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The reaction rate of propene pyrolysis was investigated based on the elementary reactions proposed in Qu et al., J Comput Chem 2009, 31, 1421. The overall reaction rate was developed with the steady-state approximation and the rate constants of the elementary reactions were determined with the variational transition state theory. For the elementary reaction having transition state, the vibrational frequencies of the selected points along the minimum energy path were calculated with density functional theory at B3PW91/6-311G(d,p) level and the energies were improved with the accurate model chemistry method G3(MP2). For the elementary reaction without transition state, the frequencies were calculated with CASSCF/6-311G(d,p) and the energies were refined with the multireference configuration interaction method MRCISD/6-311G(d,p). The rate constants were evaluated within 200-2000 K and the fitted three-parameter expressions were obtained. The results are consistent with those in the literatures in most cases. For the overall rate, it was found that the logarithm of the rate and the reciprocal temperature have excellent linear relationship above 400 K, predicting that the rate follows a typical first-order law at high temperatures of 800-2000 K, which is also consistent with the experiments. The apparent activation energy in 800-2000 K is 317.3 kJ/mol from the potential energy surface of zero Kelvin. This value is comparable with the energy barriers, 365.4 and 403.7 kJ/mol, of the rate control steps. However, the apparent activation energy, 215.7 kJ/mol, developed with the Gibbs free energy surface at 1200 K is consistent with the most recent experimental result 201.9 ± 0.6 kJ/mol.

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Section: Methodology and Modelsmentioning

confidence: 99%

Reaction rate of propene pyrolysis

Han

Liu

et al. 2011

J Comput Chem

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“…Therefore, MRCISD/6-31G(d) calculations were carried out to examine the dominant configuration by using the GAMESS 54 plus Xi'an CI [55][56][57][58][59] programs before the G3(MP2) energy evaluations. It was found that all the dominant configuration coefficients are larger than 0.86 and those for the final most favorable reaction pathways are larger than 0.9 (the detailed results are listed in Supplementary material 1).…”

Section: Methodsmentioning

confidence: 99%

Reaction pathways of propene pyrolysis

Wang

et al. 2010

J Comput Chem

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The gas-phase reaction pathways in preparing pyrolytic carbon with propene pyrolysis have been investigated in detail with a total number of 110 transition states and 50 intermediates. The structure of the species was determined with density functional theory at B3PW91/6-311G(d,p) level. The transition states and their linked intermediates were confirmed with frequency and the intrinsic reaction coordinates analyses. The elementary reactions were explored in the pathways of both direct and the radical attacking decompositions. The energy barriers and the reaction energies were determined with accurate model chemistry method at G3(MP2) level after an examination of the nondynamic electronic correlations. The heat capacities and entropies were obtained with statistical thermodynamics. The Gibbs free energies at 298.15 K for all the reaction steps were reported. Those at any temperature can be developed with classical thermodynamics by using the fitted (as a function of temperature) heat capacities. It was found that the most favorable paths are mainly in the radical attacking chain reactions. The chain was proposed with 26 reaction steps including two steps of the initialization of the chain to produce H and CH(3) radicals. For a typical temperature (1200 K) adopted in the experiments, the highest energy barriers were found in the production of C(3) to be 203.4 and 193.7 kJ/mol. The highest energy barriers for the production of C(2) and C were found 174.1 and 181.4 kJ/mol, respectively. These results are comparable with the most recent experimental observation of the apparent activation energy 201.9 +/- 0.6 or 137 +/- 25 kJ/mol.

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“…随着电子数和轨道数增多, MRCI计算很快就会变得非常耗时, 因此人们发展了众多近似CI方法, 以进一步减少计算量, 当然相关能也会有所损失. 基于空穴-粒子对应 [15] 的双收缩CI(DCCI) [11,12] 2 Abrams M L, Sherrill C D. Full configuration interaction potential energy curves for the X 1 Σ…”

Section: Mrci计算虽然能替代超大计算量的fci 但unclassified

“…本文采用的多参考态计算, 除了MRCI, 双收缩 CI(DCCI) [11,12] CASSCF的计算应用GAMESS程序 [13] , CI及其近似方法的计算应用程序Xi'an-CI [14] .…”

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