Driven similarity renormalization group: Third-order multireference perturbation theory

Li, Chenyang; Evangelista, Francesco A.

doi:10.1063/1.4979016

Cited by 50 publications

(81 citation statements)

References 132 publications

(231 reference statements)

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“…The DSRG-MRPT2 error remains fairly constant (maximum value of 32.91 mE h ), and the resulting NPE is 18.4 mE h for N 2 /cc-pVDZ . Note that the DSRG-MRPT3 improves the description of the PES of 1 Σ g + N2 computed to DSRG-MRPT2 and yields a maximum deviation 13.88 mE h with an NPE equal to 4.80 mE h . , As per the work of Li–Evangelista, the deviations of CASPT2 and NEVPT2 results from FCI ones never exceed 22.87 and 34.17 mE h with NPEs 9.5 and 1.3 mE h . Analogous trends are also observed for the IVO-BWMRPT.…”

Section: Resultsmentioning

confidence: 63%

“…As the above discussion illustrates that the IVO-BWMRPT is capable of tackling the complexity of C 2 rather well; next, we consider a demanding situation created by breaking of the triple bond in 1 Σ g + N 2 . ,,,,,,,,,,− Note that CCSD and also CCSD(T) provide an inadequate description of the bond breaking as it yields an unphysical hump on the energy surface at bond distances larger than the equilibrium one. − ,, In our current study, six electrons in six orbitals, CAS(6,6) [involving one σ and two π bonding orbitals as well as the corresponding antibonding orbitals, the smallest reasonable CAS] IVO-CASCI reference, have been used for N 2 as the dominant configuration changes from 3σ g 2 1π u 4 (excluding the first four occupied orbitals) near the equilibrium region to 3σ g 1 1π u 2 1π g 2 3σ u 1 in the dissociation region. Li and Paldus − demonstrated that for larger N–N distances than about 1.5 R e ( R e designates the experimental equilibrium bond length, 2.068 a.u.…”

Section: Resultsmentioning

confidence: 88%

“…The errors with respect to FCI in the computed PES for 1 Σ g + N 2 obtained by CASPT2, NEVPT2, and different version of DSRG-MRPT2 (driven similarity renormalization group second order MRPT) methods with cc-pVDZ can be found in Table 1 in ref . The DSRG-MRPT2 error remains fairly constant (maximum value of 32.91 mE h ), and the resulting NPE is 18.4 mE h for N 2 /cc-pVDZ . Note that the DSRG-MRPT3 improves the description of the PES of 1 Σ g + N2 computed to DSRG-MRPT2 and yields a maximum deviation 13.88 mE h with an NPE equal to 4.80 mE h . , As per the work of Li–Evangelista, the deviations of CASPT2 and NEVPT2 results from FCI ones never exceed 22.87 and 34.17 mE h with NPEs 9.5 and 1.3 mE h .…”

Section: Resultsmentioning

confidence: 94%

“…A relaxed IVO-BWMRPT version is only slightly more expensive than the corresponding unrelaxed one. Li and Evangelista 36 recently demonstrated that at the perturbative level, it is generally advantageous to incorporate reference relaxation effects for single-and multiple-bond dissociation processes. From the nature of the denominator of eq 1, it can be argued that the method is parameter-free and does not contain any threshold to circumvent numerical instabilities.…”

Section: Brillouin−wigner Second-order Perturbation Theory For Ivo-ca...mentioning

confidence: 99%

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Investigation of Multiple-Bond Dissociation Using Brillouin–Wigner Perturbation with Improved Virtual Orbitals

Chattopadhyay

2020

J. Phys. Chem. A

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An improved virtual orbital complete active space configuration interaction reference function-based multireference Brillouin–Wigner perturbation approach (IVO-BWMRPT) that avoids the numerical divergence because of the intruder problem by focusing on obtaining a single root of the many-body Hamiltonian is used to compute dissociation energy surfaces and spectroscopic constants of C2, N2, and CN radicals. For such correlated molecules, the computational demand to delineate the wavefunction exactly is quite challenging. The IVO-BWMRPT method, a convenient and effective way to handle quasidegenerate situations, accurately captures different correlations and is capable of treating the variation of multiconfigurational nature of wave functions that occur during the multiple-bond breaking processes. Spectroscopic constants extracted from the computed surface are in good agreement with experimental or benchmark results, indicating that the components of the IVO-BWMRPT scheme must perform in harmony for providing a well-behaved and consistent description of all computed bond lengths.

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Section: Resultsmentioning

confidence: 63%

Section: Resultsmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 94%

Section: Brillouin−wigner Second-order Perturbation Theory For Ivo-ca...mentioning

confidence: 99%

See 2 more Smart Citations

Investigation of Multiple-Bond Dissociation Using Brillouin–Wigner Perturbation with Improved Virtual Orbitals

Chattopadhyay

2020

J. Phys. Chem. A

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“…The equilibrium geometry of C 2 H 6 was taken from Ref. 60. In ppTDA@DFA, ppTDA@RS-DFA, CCSD calculations, the total energies at the bond length 5.0Å, 6.0Å, 4.0Å, 5.0A were set as zero for LiH, BH, CH + , C 2 H 4 respectively.…”

mentioning

confidence: 99%

Multireference Density Functional Theory for Describing Ground and Excited States with Renormalized Singles

Li,

Chen,

Yang

2021

Preprint

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We applied renormalized singles (RS) in the multireference density functional theory (DFT) approach to calculate accurate electronic energies of ground states and excited states for molecular systems. The multireference DFT approach, developed recently, determines the total energy of the N -electron system as the sum of the (N − 2)electron energy from a density functional approximation (DFA) and the two-electron addition excitation energies from the particle-particle Tamm-Dancoff approximation (ppTDA) linear response approach. The ppTDA@RS-DFA approach first constructs the RS Hamiltonian to capture all singles contributions of the (N −2)-electron auxiliary system described by a chosen DFA. Then the RS Hamiltonian is used in ppTDA to calculate two-electron addition excitation energies. The total energy is optimized with the optimized effective potential (OEP) method. The multireference description of both the ground and excited states of the N -electron systems comes naturally through the linear response theory. We show that the ppTDA@RS-DFA approach provides considerable improvement over the ppTDA@DFA, the original approach without using RS, and describes both ground state and excited state properties accurately, with electron densities preserving the proper symmetry for systems having strong (static) correlation. For ground states, ppTDA@RS-DFA properly describes dissociation energies, equilibrium bond lengths and the dissociation curves of all tested molecules, and the double bond rotation of ethylene. For excited states, ppTDA@RS-DFA provides accurate excitation energies of molecular systems and largely eliminates the dependence on the choice of the DFA. ppTDA@RS-DFA thus provides a promising and very efficient multireference approach to systems with static correlation.

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Ab Initio Methods in First‐Row Transition Metal Chemistry

Feldt

Phung

2022

Eur J Inorg Chem

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Molecules containing 3d transition metals (TMs) are usually associated with versatile reactivity, partly due to their complicated electronic structures involving multiple close‐lying spin states. An accurate description of different electronic states is notoriously difficult and still a challenge for computational methodologies. Density functional theory, although repeatedly shown to give less reliable results for near‐degeneracy problems, remains the workhorse to explore the reactivity of TM complexes. Ab initio wavefunction theory has been lagging behind due to its high computational cost. However, tremendous efforts have been put to improve their applicability over the past few years, particularly local coupled cluster and low‐scaling multireference methods. In this mini‐review, we highlight major advancements of these ab initio techniques and discuss their recent applications in the calculations of spin state energetics of first‐row TM complexes, ranging from spin crossover compounds and metalloproteins to biomimetic complexes capable of activating C−H bonds.

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Driven similarity renormalization group: Third-order multireference perturbation theory

Cited by 50 publications

References 132 publications

Investigation of Multiple-Bond Dissociation Using Brillouin–Wigner Perturbation with Improved Virtual Orbitals

Investigation of Multiple-Bond Dissociation Using Brillouin–Wigner Perturbation with Improved Virtual Orbitals

Multireference Density Functional Theory for Describing Ground and Excited States with Renormalized Singles

Ab Initio Methods in First‐Row Transition Metal Chemistry

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