Negative ion photoelectron spectroscopy of chromium dimer

Casey, Sean M.; Leopold, D. G.

doi:10.1021/j100106a005

Cited by 200 publications

(203 citation statements)

References 13 publications

(20 reference statements)

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“…66 The spectroscopic constants are shown in Table Table 1. Our obtained CBS D e of 1.43eV is very close to the inferred experimental binding energy of 1.47 eV from the negative ion photoelectron spectroscopy measurements of Casey and Leopold, 90 while the bond-length and vibrational frequency also agree Cr 2 DMRG-SC-NEVPT2(12e,22o) potential energy curve cc-pwCVTZ-DK cc-pwCVQZ-DK cc-pwCV5Z-DK CBS limit Expt. curve is from Ref.…”

Section: Chromium Dimersupporting

confidence: 86%

“…We find that using larger basis sets together with this small active space indeed yields far too deep a curve, in agreement with earlier studies using atomic natural orbital (ANO) basis sets. 68 90 We then extended the (12e,12o) active space by adding another set of σ , π, π , δ , δ orbitals and their corresponding anti-bonding orbitals to obtain a (12e,22o) active space. We selected the orbitals from the converged (12e,12o) CASSCF calculation based on symmetry and their orbital energies, and the orbitals were then further optimized using DMRG-CASSCF (M=1000, no frozen core).…”

Section: Chromium Dimermentioning

confidence: 99%

“…69 The experimental curve is taken from Ref. 90 well. It is remarkable to see that even with the largest cc-pwCV5Z-DK basis, the binding energy is still 0.14 eV away from the CBS limit, demonstrating the very large basis set effects in this system.…”

Section: Chromium Dimermentioning

confidence: 99%

See 2 more Smart Citations

N-Electron Valence State Perturbation Theory Based on a Density Matrix Renormalization Group Reference Function, with Applications to the Chromium Dimer and a Trimer Model of Poly(p-Phenylenevinylene)

Guo

Watson

et al. 2016

J. Chem. Theory Comput.

173

215

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The strongly-contracted variant of second order N-electron valence state perturbation theory (NEVPT2) is an efficient perturbative method to treat dynamic correlation without the problems of intruder states or level shifts, while the density matrix renormalization group (DMRG) provides the capability to tackle static correlation in large active spaces. We present a combination of the DMRG and strongly-contracted NEVPT2 (DMRG-SC-NEVPT2) that uses an efficient algorithm to compute high order reduced density matrices from DMRG wave functions. The capabilities of DMRG-SC-NEVPT2 are demonstrated on calculations of the chromium dimer potential energy curve at the basis set limit, and the excitation energies of poly-p-phenylene vinylene trimer (PPV(n=3)).

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Section: Chromium Dimersupporting

confidence: 86%

Section: Chromium Dimermentioning

confidence: 99%

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N-Electron Valence State Perturbation Theory Based on a Density Matrix Renormalization Group Reference Function, with Applications to the Chromium Dimer and a Trimer Model of Poly(p-Phenylenevinylene)

Guo

Watson

et al. 2016

J. Chem. Theory Comput.

173

215

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“…As noted in Ref. 3, there were large gaps in the vibrational data between 3040 and 4880 cm −1 , which insufficiently constrained the shape of the potential in this region. The possibility was TABLE I. Spectroscopic constants of Cr2 computed using phaseless and free-projection AFQMC methods, extrapolated to the CBS limit.…”

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confidence: 87%

An auxiliary-field quantum Monte Carlo study of the chromium dimer

Purwanto

Zhang

Krakauer

2015

The Journal of Chemical Physics

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The chromium dimer (Cr2) presents an outstanding challenge for many-body electronic structure methods. Its complicated nature of binding, with a formal sextuple bond and an unusual potential energy curve, is emblematic of the competing tendencies and delicate balance found in many strongly correlated materials. We present a nearexact calculation of the potential energy curve (PEC) and ground state properties of Cr2, using the auxiliary-field quantum Monte Carlo (AFQMC) method. Unconstrained, exact AFQMC calculations are first carried out for a medium-sized but realistic basis set. Elimination of the remaining finite-basis errors and extrapolation to the complete basis set (CBS) limit is then achieved with a combination of phaseless and exact AFQMC calculations. Final results for the PEC and spectroscopic constants are in excellent agreement with experiment. The chromium dimer is a strongly correlated molecule which poses a formidable challenge to even the most accurate many-body methods. It features a formal sextuple bond, with a weak binding energy (∼ 1.5 eV), a short equilibrium bond length (∼ 1.7Å), and an unusual "shoulder" structure in its potential energy curve (PEC). [1][2][3] The ground state of Cr 2 is highly multiconfigurational, and proper theoretical description requires an accurate treatment of the strong 3d electron correlations (both static and dynamic). The nature of the PEC in Cr 2 is representative of the competing tendencies separated by small energy differences seen in many strongly correlated materials. Because of the fundamental and technological significance of such materials, improving our abilities for accurate calculations in strongly correlated systems is one of the most pressing needs in condensed matter physics and quantum chemistry.Standard quantum chemistry methods, such as density functional theory (DFT), Hartree-Fock (HF), and post-HF methods such as single-reference second-order Møller-Plesset perturbation theory (MP2) and single-reference coupled cluster with singles, doubles, and perturbative triples [CCSD(T)], all fail to describe the correct binding of Cr 2 . Representative standard quantum chemistry results are shown in Fig. 1. As often is the case, the DFT results vary greatly, depending on the choice of exchange-correlation functional. There have also been numerous attempts to calculate the PEC of Cr 2 using sophisticated multireference quantum chemistry methods, 4-9 including the complete active space second-order perturbation theory (CASPT2) 10-12 and, more recently, CASPT2 based on a large density matrix renormalization group (DMRG) reference wave function (DMRG-CASPT2). 13 These calculations obtain qualitatively correct binding, but the results are sensitive to choice of active space and/or basis set. Standard quantum Monte Carlo (QMC) approaches 14,15 have also been severely challenged. A recent fixed-node diffusion Monte Carlo (DMC) study, which examined the use of a variety of single-and multi-determinant trial wave functions, did not obtain satisfactory binding (i...

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“…The experimental equilibrium distance of Cr 2 is 1.68 Å [14] [16]) is not so stable for the sixfold bonding. In addition, a double-well-like potential curve observed by experiment shows a weak attractive energy even at 3.0 Å [23].…”

Section: Potential Energy Curvesmentioning

confidence: 84%

BS DFT and BS HDFT studies of CrCr sextuple bond from the viewpoint of electron correlation effects

Kitagawa

Nakanishi

Saitô

et al. 2009

Int J of Quantum Chemistry

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ABSTRACT:The nature of CrOCr bond and effectiveness of broken-symmetry (BS) density functional theory (DFT) and hybrid DFT (HDFT) methods are examined in terms of electron correlation effects. Two types of correlation energies, i.e., static and dynamical correlation energies are estimated by relative energy curves and correlation energy curves. Energy decomposition analyses and natural orbital analyses reveal how these electron correlation effects affect the CrOCr bonding. In addition, the effect of those effects to an energy gap between the lowest spin (LS) state (S ϭ 0) and the highest spin (HS) state (S ϭ 6) is also discussed with respect to calculations of effective exchange integrals (J).

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Negative ion photoelectron spectroscopy of chromium dimer

Cited by 200 publications

References 13 publications

N-Electron Valence State Perturbation Theory Based on a Density Matrix Renormalization Group Reference Function, with Applications to the Chromium Dimer and a Trimer Model of Poly(p-Phenylenevinylene)

N-Electron Valence State Perturbation Theory Based on a Density Matrix Renormalization Group Reference Function, with Applications to the Chromium Dimer and a Trimer Model of Poly(p-Phenylenevinylene)

An auxiliary-field quantum Monte Carlo study of the chromium dimer

BS DFT and BS HDFT studies of CrCr sextuple bond from the viewpoint of electron correlation effects

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