Exactly-embedded multiconfigurational self-consistent field theory using density matrix embedding: the localized active space self-consistent field method

Abstract

Density matrix embedding theory (DMET) is a fully quantum-mechanical embedding method which shows great promise as a method of defeating the inherent exponential cost scaling of multiconfigurational wave function-based calculations by breaking large systems into smaller, coupled subsystems. However, we recently [JCTC 2018, 14, 1960] encountered evidence that the single-determinantal bath picture inherent to DMET is sometimes problematic when the complete active space self-consistent field (CASSCF) is used as a solver and the method is applied to realistic models of strongly-correlated molecules. Here, we show this problem can be defeated by generalizing DMET to use a multiconfigurational wave function as a bath without sacrificing attractive features of DMET, such as a second-quantized embedded subsystem Hamiltonian, by dividing the active space into unentangled active subspaces each localized to one fragment. We introduce the term localized active space (LAS) to refer to this kind of wave function. We obtain the LAS wave function by the DMET algorithm itself self-consistently, and we name this approach the localized active space self-consistent field (LASSCF) method. LASSCF exploits a modified DMET algorithm, but it requires no ambiguous error function minimization, produces a wave function with exact embedding, is variational, and reproduces CASSCF where comparable DMET calculations fail. Our results for test calculations on the nitrogen double-bond dissociation potential energy curves of several diazene molecules suggest that LASSCF can be an appropriate starting point for a perturbative treatment. Outside of the context of embedding, LAS is an attractive alternative to a CAS wave function because its cost scaling is exponential only with respect to the size of individual fragment active subspaces, rather than the whole active space of the entire system.

References in corpus (16)

• Density matrix embedding: A simple alternative to dynamical mean-field theory
• Density matrix embedding: A strong-coupling quantum embedding theory
• Quantum embedding theories
• A practical guide to density matrix embedding theory in quantum chemistry
• Automated construction of molecular active spaces from atomic valence orbitals
• Computational characterization and prediction of metal-organic framework properties
• Entanglement in solvable many-particle models
• Density Matrix Embedding from Broken Symmetry Lattice Mean-Fields
• Electron correlation in solids via density embedding theory
• Systematically improvable multi-scale solver for correlated electron systems
• Can Density Matrix Embedding Theory with the Complete Activate Space Self-Consistent Field Solver Describe Single and Double Bond Breaking in Molecular Systems?
• Cluster Density Matrix Embedding Theory for Quantum Spin Systems
• Density matrix embedding theory for interacting electron-phonon systems
• Five years of density matrix embedding theory
• Block product density matrix embedding theory for strongly correlated spin systems
• Incremental Embedding: A Density Matrix Embedding Scheme for Molecules

Cited by in corpus (33)

• Recent developments in the PySCF program package
• The Density Matrix Renormalization Group in Chemistry and Molecular Physics: Recent Developments and New Challenges
• Excited state, non-adiabatic dynamics of large photoswitchable molecules using a chemically transferable machine learning potential
• Quantum-centric Supercomputing for Materials Science: A Perspective on Challenges and Future Directions
• Green's function formulation of quantum defect embedding theory
• Selected Configuration Interaction in a Basis of Cluster State Tensor Products
• The Variational Localized Active Space Self-Consistent Field Method
• Matrix product states with large sites
• Simulating the electronic structure of spin defects on quantum computers
• Generalization of intrinsic orbitals to Kramers-paired quaternion spinors, molecular fragments and valence virtual spinors
• Orbital transformations to reduce the 1-norm of the electronic structure Hamiltonian for quantum computing applications
• Ab initio Quantum Simulation of Strongly Correlated Materials with Quantum Embedding
• On the effective reconstruction of expectation values from ab initio quantum embedding
• Householder transformed density matrix functional embedding theory
• Coupled cluster and perturbation theories based on a cluster mean-field reference applied to strongly correlated spin systems
• Multi-site Reaction Dynamics Through Multi-fragment Density Matrix Embedding
• Projected site-occupation embedding theory
• A static quantum embedding scheme based on coupled cluster theory
• MBE-CASSCF Approach for the Accurate Treatment of Large Active Spaces
• Symmetry-projected cluster mean-field theory applied to spin systems
• A unified density-matrix functional construction of quantum baths in density matrix embedding theory beyond the mean-field approximation
• Comparative study of the density matrix embedding theory for the Hubbard models
• MC-PDFT Nuclear Gradients and L-PDFT Energies with Meta and Hybrid Meta On-Top Functionals for Ground- and Excited-State Geometry Optimization and Vertical Excitation Energies
• FragPT2: Multi-Fragment Wavefunction Embedding with Perturbative Interactions
• Efficient simulation of inhomogeneously correlated systems using block interaction product states
• Distinguishing homolytic versus heterolytic bond dissociation of phenyl sulfonium cations with localized active space methods
• On the pure state $v$-representability of density matrix embedding theory
• Local Potential Functional Embedding Theory of Molecular Systems: Localized Orbital-Based Embedding from an Exact Density-Functional Perspective
• A versatile unitary transformation framework for an optimal bath construction in density-matrix based quantum embedding approaches
• Piecewise Interaction Picture Density Matrix Quantum Monte Carlo
• Effective Hamiltonians from Spin Adapted Configuration Interaction
• Addressing Strong Correlation by Approximate Coupled-Pair Methods with Active-Space and Full Treatments of Three-Body Clusters
• $i$CAS: Imposed Automatic Selection and Localization of Complete Active Spaces