TY - JOUR
T1 - High-level ab initio predictions for the ionization energy, bond dissociation energies, and heats of formation of cobalt carbide (CoC) and its cation (CoC+)
AU - Lau, Kai-Chung
AU - Pan, Yi
AU - Lam, Chow-Shing
AU - Huang, Huang
AU - Chang, Yih-Chung
AU - Luo, Zhihong
AU - Shi, Xiaoyu
AU - Ng, C. Y.
PY - 2013/3/7
Y1 - 2013/3/7
N2 - The ionization energy (IE) of CoC and the 0 K bond dissociation energies (D0) and the heats of formation at 0 K (ΔH°f0) and 298 K (ΔH°f298) for CoC and CoC+ are predicted by the wavefunction based coupled-cluster theory with single, double, triple and quadruple excitations (CCSDTQ) and complete basis set (CBS) approach. The CCSDTQ/CBS calculations presented here involve the approximation to the CBS limit at the coupled cluster level up to full quadruple excitations along with the zero-point vibrational energy, high-order correlation, core-valence (CV) electronic, spin-orbit coupling, and scalar relativistic effect corrections. The present calculations provide the correct symmetry, 1Σ+, for the ground state of CoC+. The CCSDTQ/CBS IE(CoC) = 7.740 eV is found in good agreement with the experimental IE value of 7.73467 ± 0.00007 eV, determined in a two-color laser photoion and pulsed field ionization-photoelectron study. This work together with the previous experimental and theoretical investigations support the conclusion that the CCSDTQ/CBS method is capable of providing reliable IE predictions for 3d-transition metal carbides, such as FeC, CoC, and NiC. Among the single-reference based coupled-cluster methods and multi-reference configuration interaction (MRCI) approach, the CCSDTQ and MRCI methods give the best predictions to the harmonic frequencies ωe (ωe+) = 956 (992) and 976 (1004) cm-1 and the bond lengths re (re+) = 1.560 (1.528) and 1.550 (1.522) Å, respectively, for CoC (CoC+) in comparison with the experimental values. The CCSDTQ/CBS calculations give the prediction of D0(Co+-C) - D0(Co-C) = 0.175 eV, which is also consistent with the experimental determination of 0.14630 ± 0.00014 eV. The theoretical results show that the CV and valence-valence electronic correlations beyond CCSD(T) wavefunction and the relativistic effect make significant contributions to the calculated thermochemical properties of CoC/CoC+. For the experimental D0 and ΔH°f0 values of CoC/CoC+, which are not known experimentally, we recommend the following CCSDTQ/CBS predictions: ΔH°f0(CoC) = 775.7 kJ/mol and ΔH°f0(CoC+) = 1522.5 kJ/mol, ΔH°f298(CoC) = 779.2 kJ/mol and ΔH°298(CoC+) = 1526.0 kJ/mol. © 2013 American Institute of Physics.
AB - The ionization energy (IE) of CoC and the 0 K bond dissociation energies (D0) and the heats of formation at 0 K (ΔH°f0) and 298 K (ΔH°f298) for CoC and CoC+ are predicted by the wavefunction based coupled-cluster theory with single, double, triple and quadruple excitations (CCSDTQ) and complete basis set (CBS) approach. The CCSDTQ/CBS calculations presented here involve the approximation to the CBS limit at the coupled cluster level up to full quadruple excitations along with the zero-point vibrational energy, high-order correlation, core-valence (CV) electronic, spin-orbit coupling, and scalar relativistic effect corrections. The present calculations provide the correct symmetry, 1Σ+, for the ground state of CoC+. The CCSDTQ/CBS IE(CoC) = 7.740 eV is found in good agreement with the experimental IE value of 7.73467 ± 0.00007 eV, determined in a two-color laser photoion and pulsed field ionization-photoelectron study. This work together with the previous experimental and theoretical investigations support the conclusion that the CCSDTQ/CBS method is capable of providing reliable IE predictions for 3d-transition metal carbides, such as FeC, CoC, and NiC. Among the single-reference based coupled-cluster methods and multi-reference configuration interaction (MRCI) approach, the CCSDTQ and MRCI methods give the best predictions to the harmonic frequencies ωe (ωe+) = 956 (992) and 976 (1004) cm-1 and the bond lengths re (re+) = 1.560 (1.528) and 1.550 (1.522) Å, respectively, for CoC (CoC+) in comparison with the experimental values. The CCSDTQ/CBS calculations give the prediction of D0(Co+-C) - D0(Co-C) = 0.175 eV, which is also consistent with the experimental determination of 0.14630 ± 0.00014 eV. The theoretical results show that the CV and valence-valence electronic correlations beyond CCSD(T) wavefunction and the relativistic effect make significant contributions to the calculated thermochemical properties of CoC/CoC+. For the experimental D0 and ΔH°f0 values of CoC/CoC+, which are not known experimentally, we recommend the following CCSDTQ/CBS predictions: ΔH°f0(CoC) = 775.7 kJ/mol and ΔH°f0(CoC+) = 1522.5 kJ/mol, ΔH°f298(CoC) = 779.2 kJ/mol and ΔH°298(CoC+) = 1526.0 kJ/mol. © 2013 American Institute of Physics.
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U2 - 10.1063/1.4792718
DO - 10.1063/1.4792718
M3 - RGC 21 - Publication in refereed journal
C2 - 23485289
VL - 138
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
SN - 0021-9606
IS - 9
M1 - 094302
ER -