Electronic structure of strongly correlated systems: recent developments in multiconfiguration pair-density functional theory and multiconfiguration nonclassical-energy functional theory

Zhou, Chen; Hermes, Matthew R.; Wu, Dihua; Bao, Jie J.; Pandharkar, Riddhish; King, Daniel R.; Zhang, Dayou; Scott, Thais R.; Lykhin, Aleksandr O.; Gagliardi, Laura; Truhlar, Donald G.

doi:10.1039/d2sc01022d

Cited by 31 publications

(39 citation statements)

References 155 publications

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“…This result is important because knowledge of | E / D | and the g tensor is useful to recognize important spin systems ,− Thus, using the (2,5) active space and MS-CASPT2 or the HMS-PDFT(tPBE0) method can provide a good initial exploration of molecular qubit candidates. It is encouraging that HMS-PDFT(tPBE0) provides the same qualitative information as MS-CASPT2, but at a lower computational cost as observed in several studies for a wide range of molecules and properties (more information available in ref ). Hence, it may be affordable to explore larger molecular systems with this method.…”

Section: Resultsmentioning

confidence: 61%

“… 52 − 57 The MC-PDFT or MS-PDFT computational cost is similar to that of computing the reference wave function. 58 MS-PDFT has recently been successfully used to study the g tensor 59 and the ZFS 46 of several transition metal complexes.…”

Section: Theoretical Frameworkmentioning

confidence: 99%

“…To quantitatively describe dynamic electron correlation in chemical systems, a post-SA-CASSCF calculation is performed, using multistate complete-active-space second-order perturbation theory (MS-CASPT2), multiconfiguration pair-density functional theory (MC-PDFT), or multistate pair-density functional theory (MS-PDFT). MC-PDFT and MS-PDFT are methods that provide CASPT2-quality and MS-CASPT2-quality accuracy at reduced computational cost. − The MC-PDFT or MS-PDFT computational cost is similar to that of computing the reference wave function . MS-PDFT has recently been successfully used to study the g tensor and the ZFS of several transition metal complexes.…”

Section: Theoretical Frameworkmentioning

confidence: 99%

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Multiconfiguration Pair-Density Functional Theory for Chromium(IV) Molecular Qubits

Vega

Pandharkar

Stroscio

et al. 2022

JACS Au

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Pseudotetrahedral organometallic complexes containing chromium(IV) and aryl ligands have been experimentally identified as promising molecular qubit candidates. Here we present a computational protocol based on multiconfiguration pair-density functional theory for computing singlet–triplet gaps and zero-field splitting (ZFS) parameters in Cr(IV) aryl complexes. We find that two multireference methods, multistate complete active space second-order perturbation theory (MS-CASPT2) and hybrid multistate pair-density functional theory (HMS-PDFT), perform better than Kohn–Sham density functional theory for singlet–triplet gaps. Despite the very small values of the ZFS parameters, both multireference methods performed qualitatively well. MS-CASPT2 and HMS-PDFT performed particularly well for predicting the trend in the ratio of the rhombic and axial ZFS parameters, | E / D |. We have also investigated the dependence and sensitivity of the calculated ZFS parameters on the active space and the molecular geometry. The methodologies outlined here can guide future prediction of ZFS parameters in molecular qubit candidates.

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Section: Resultsmentioning

confidence: 61%

Section: Theoretical Frameworkmentioning

confidence: 99%

Section: Theoretical Frameworkmentioning

confidence: 99%

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Multiconfiguration Pair-Density Functional Theory for Chromium(IV) Molecular Qubits

Vega

Pandharkar

Stroscio

et al. 2022

JACS Au

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“…where S, D, F, I are respectively the full overlap, density, Fock and identity matrices, λ is a parameter which damps out to 0 eventually during the SCF iteration, D α,β E refers to the spin-resolved truncated density matrix of the environment, and D E = D α E + D β E refers to the spin-summed one, as defined in Eq. (3). With the density matrices we define the (environment) spin polarization entropy ∆S E , which vanishes identically if D α E = D β E (i.e.…”

Section: ĥZfs = D ŝ2mentioning

confidence: 99%

Efficient multi-configurational quantum chemistry approach to single-ion magnets based on density matrix embedding theory

Sun

Jiang

2022

Preprint

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Density matrix embedding theory (DMET) provides a systematic framework to combine low-level (e.g. Hartree-Fock approximation) and high-level correlated quantum chemistry methods to treat strongly correlated systems with remarkable accuracy and efficiency. In this work, we proposed an efficient quantum embedding approach that uses the restricted open-shell Hartree-Fock (ROHF) as the low level solver and combines DMET with the complete active space self-consistent field and subsequent state interaction treatment of spin-orbit coupling (CASSI-SO), and applied it to theoretical description of single-ion magnets (SIMs). We have developed a novel direct inversion of iterative subspace (DIIS) technique that incorporates a regularization term related to the spin polarization entropy, termed as R-DIIS, and ensures ROHF to converge to physically correct ground state, which is found to be crucial for the efficacy of subsequent CASSI-SO calculation. We found that the DMET+CASSI-SO approach can produce reliable zero-field splitting (ZFS) parameters in typical 3d-SIMs with dramatically reduced computational cost compared to its all-electron counterpart. This work therefore demonstrates the great potential of the DMET-based CASSI-SO approach for efficient \textit{ab initio} study of magneto-structural correlations in complex molecular magnetic systems.

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“…In those cases, the R-DIIS technique may play more important roles in helping to escape local minima during SCF calculations. We also expect that our work will inspire future development of DMET-based multireference methods that incorporate dynamical correlation , with improved efficiency. Further exploration of the role played by the spin polarization entropy in the applications of DMET framework to open-shell systems may also be of great interest and might lead to novel insights into quantum embedding theory in general.…”

mentioning

confidence: 99%

Efficient Multiconfigurational Quantum Chemistry Approach to Single-Ion Magnets Based on Density Matrix Embedding Theory

Sun

Jiang

2022

J. Phys. Chem. Lett.

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Density matrix embedding theory (DMET) provides a systematic framework to combine low-level (e.g., Hartree−Fock approximation) and high-level correlated quantum chemistry methods to treat strongly correlated systems. In this work, we propose an efficient quantum embedding approach that combines DMET with the complete active space self-consistent field and subsequent state interaction treatment of spin−orbit coupling (CASSI-SO) and apply it to a theoretical description of single-ion magnets (SIMs). We have developed a novel regularized direct inversion of iterative subspace (R-DIIS) technique that ensures restricted open-shell Hartree−Fock converging to a physically correct ground state, which is found to be crucial for the efficacy of subsequent CASSI-SO calculation. The DMET +CASSI-SO approach can produce reliable zero-field splitting parameters in typical 3d-SIMs with dramatically reduced computational cost compared to its all-electron counterpart. This work therefore demonstrates the great potential of DMET-based multiconfigurational approaches for efficient ab initio study of magneto−structural correlations in complex molecular magnetic systems.

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Electronic structure of strongly correlated systems: recent developments in multiconfiguration pair-density functional theory and multiconfiguration nonclassical-energy functional theory

Abstract: Strong electron correlation plays an important role in transition-metal and heavy-metal chemistry, magnetic molecules, bond breaking, biradicals, excited states, and many functional materials, but it provides a significant challenge for...

Cited by 31 publications

References 155 publications

Multiconfiguration Pair-Density Functional Theory for Chromium(IV) Molecular Qubits

Multiconfiguration Pair-Density Functional Theory for Chromium(IV) Molecular Qubits

Efficient multi-configurational quantum chemistry approach to single-ion magnets based on density matrix embedding theory

Efficient Multiconfigurational Quantum Chemistry Approach to Single-Ion Magnets Based on Density Matrix Embedding Theory

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