“…Hypothesizing again additivity of the core effects with respect to the bond distance, our best estimate for r e is 2.331 − 0.026 = 2.305 Å. Relative results obtained from ref are D e = 83.7 kcal/mol and r e = 2.341 Å at the MRCI level of theory. …”
Section: Resultsmentioning
confidence: 57%
“…Corresponding theoretical values from refs and are 45.9 kcal/mol, 2.348 Å and 45.4 kcal/mol, 2.368 Å, respectively. Our total energies of X 3 Σ - and a 5 Σ - states are 29 and 26 mE h lower than those reported in ref .…”
Section: Resultsmentioning
confidence: 79%
“…Shifting upward the 3 Σ - PEC uniformly by 0.130 eV, to match the experimental CaC ( 3 P← 1 S) energy splitting, the energy separation becomes 1500 + 1048 = 2548 cm -1 , suggesting that the T e (a 5 Σ - ← X 3 Σ - ) is bracketed between 1500 and 2548 cm -1 . The corresponding UCCSD(T) result of Serrano and Canuto 6 is 800 cm -1 , and the MRCI of Takada et al, 695 cm -1 . In the MgC system the ground state is also of 3 Σ - symmetry, the energy separation T e ( 5 Σ - ← 3 Σ - ) being 3545 cm -1 at the MRCI + Davidson correction level .…”
Section: Resultsmentioning
confidence: 84%
“…In this work, and for reasons of comparison, we also report some results from the present study, where it is clearly indicated that the ground state of CaC is of 3 Σ - symmetry (see also below). Interestingly, two more papers on CaC appeared at the same time as ref : the experimental one previously mentioned, and a theoretical work by Takada et al These workers employed a multireference + singles + doubles configuration interaction approach coupled with a 6-311G(3d1f) basis, and a selection scheme of picking configurations. They report results on the disputed 3 Σ - and 5 Σ - states as well as on four higher states, namely, 3 Π, 1 Δ, 1 Π, and 1 Σ + .…”
Using multireference methods and semiquantitative basis sets, we have computed nineteen potential energy
curves and spectroscopic parameters of the calcium monocarbide system, CaC. For the much debated 3Σ-
and 5Σ- states our calculations definitively show that the ground state is of 3Σ- symmetry with the a5Σ- state
lying 1500−2500 cm-1 higher. For the X3Σ- state our best estimates for the binding energy and equilibrium
bond length are 51 kcal/mol and 2.33 Å, respectively. All states are strongly ionic with a charge transfer of
0.5 to 0.7 e- from Ca to C.
“…Hypothesizing again additivity of the core effects with respect to the bond distance, our best estimate for r e is 2.331 − 0.026 = 2.305 Å. Relative results obtained from ref are D e = 83.7 kcal/mol and r e = 2.341 Å at the MRCI level of theory. …”
Section: Resultsmentioning
confidence: 57%
“…Corresponding theoretical values from refs and are 45.9 kcal/mol, 2.348 Å and 45.4 kcal/mol, 2.368 Å, respectively. Our total energies of X 3 Σ - and a 5 Σ - states are 29 and 26 mE h lower than those reported in ref .…”
Section: Resultsmentioning
confidence: 79%
“…Shifting upward the 3 Σ - PEC uniformly by 0.130 eV, to match the experimental CaC ( 3 P← 1 S) energy splitting, the energy separation becomes 1500 + 1048 = 2548 cm -1 , suggesting that the T e (a 5 Σ - ← X 3 Σ - ) is bracketed between 1500 and 2548 cm -1 . The corresponding UCCSD(T) result of Serrano and Canuto 6 is 800 cm -1 , and the MRCI of Takada et al, 695 cm -1 . In the MgC system the ground state is also of 3 Σ - symmetry, the energy separation T e ( 5 Σ - ← 3 Σ - ) being 3545 cm -1 at the MRCI + Davidson correction level .…”
Section: Resultsmentioning
confidence: 84%
“…In this work, and for reasons of comparison, we also report some results from the present study, where it is clearly indicated that the ground state of CaC is of 3 Σ - symmetry (see also below). Interestingly, two more papers on CaC appeared at the same time as ref : the experimental one previously mentioned, and a theoretical work by Takada et al These workers employed a multireference + singles + doubles configuration interaction approach coupled with a 6-311G(3d1f) basis, and a selection scheme of picking configurations. They report results on the disputed 3 Σ - and 5 Σ - states as well as on four higher states, namely, 3 Π, 1 Δ, 1 Π, and 1 Σ + .…”
Using multireference methods and semiquantitative basis sets, we have computed nineteen potential energy
curves and spectroscopic parameters of the calcium monocarbide system, CaC. For the much debated 3Σ-
and 5Σ- states our calculations definitively show that the ground state is of 3Σ- symmetry with the a5Σ- state
lying 1500−2500 cm-1 higher. For the X3Σ- state our best estimates for the binding energy and equilibrium
bond length are 51 kcal/mol and 2.33 Å, respectively. All states are strongly ionic with a charge transfer of
0.5 to 0.7 e- from Ca to C.
“…This is not the case, however, for CaC or BeC . In particular, for CaC, only very recently and after some controversy, theory showed , and experiment confirmed 9 that the 3 Σ - is indeed the ground state. In all three carbides MC (M = Be, Mg, and Ca) the 3 Σ - correlates to M(ns 2 ; 1 S) + C( 3 P), with a strongly competitive 5 Σ - state correlating to M( n s 1 n p 1 ; 3 P) + C( 3 P).…”
The experimentally unknown molecule ZnC has been studied using multireference methods in conjunction
with quantitative basis sets. Full potential energy curves have been constructed for the ground (X 3Σ-) state
and 29 excited states, focusing mainly on dissociation energies and bonding mechanisms. The X 3Σ- state of
ZnC has a binding energy of 26.1 kcal/mol at the internally contracted multireference−(valence) configuration
interaction level of theory (MRCI), whereas this value reduces to 23.3 kcal/mol upon including core−valence
correlation effects (3d10 of Zn) plus one-electron Douglas−Kroll relativistic corrections.
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