Themed collection Correlated electronic structure

A summary of the research themes covered during the 2024 Faraday Discussion on Correlated electronic structure and the author’s perspective on the challenges and open frontiers of the field.

We examine Lindgren's normal-ordered exponential ansatz to correlate specific spin states using spin-free excitation operators, with the aid of automatic equation generation software.

The superconducting electron localization can be obtained from a common solid-state calculation, where correlation is introduced as a redistribution of electrons around the Fermi level. This is applied to two typical superconductors, H₃S and LaH₁₀.

Application of periodic coupled-cluster theory for CO adsorption energies on the Pt(111) surface. The adsorption energy at the top site is mainly electrostatic, while at the fcc site it is correlation-based. This difference might account for the challenges DFT faces with the CO puzzle.

The use of overlapping atom-centered impurity fragments in recently-developed ab initio all-orbital DMFT, where all local orbitals within the impurity are treated with high-level quantum chemistry impurity solvers, is investigated.

Numerical results demonstrate that highly accurate energies can be achieved with a compact quantum-compatible ansatz for both weak and strong correlation in the Hubbard model, and the repulsive pairing Hamiltonian.

We describe the problems of quantum chemistry, the intuition behind classical heuristic methods used to solve them, a conjectured form of the classical complexity of quantum chemistry problems, and the subsequent opportunities for quantum advantage.

We present a discussion of explicit correlation approaches which address the nagging problem of dealing with static and dynamic electron correlation in multi-configurational active-space approaches.

Efficient multi-state interpolation of many-body wavefunctions enables rigorous nonadiabatic molecular dynamics with analytical forces and nonadiabatic coupling vectors.

We present a series of algorithmic changes that can be used to accelerate the MR-CCMC algorithm in particular and QMC algorithms in general.

A detailed classification scheme for the excited states of diradicals is presented highlighting the connections between the states of closed-shell and open-shell molecules.

We present the first application to real molecular systems of the recently proposed linear-response theory for the density-based basis-set correction method [J. Chem. Phys., 158, 234107 (2023)].

We explore ways to reduce the factorial scaling of the site permutation space in polynuclear transition metal clusters, by combining permutation and point group symmetry arguments, and using commutation relations between the cumulative partial spin and the Hamiltonian operators.

In this work, we extend the ghost Gutzwiller (gGut) framework to strongly correlated molecules, for which it holds special promise.

Combining the transcorrelated method with adaptive quantum ansätze in the context of variational quantum imaginary time evolution significantly reduces the necessary circuit depth and width for performing accurate quantum chemistry using quantum computers.

QIT offers a comprehensive toolbox for electron correlation analysis, and development of new methods for solving the electronic problem. QChem in turn provides a platform to realize quantum technology, and supplies the valuable resource of quantum entanglement in molecules.

We present a combination of the bi-orthogonal orbital optimisation framework with the recently introduced xTC version of transcorrelation.

We aim not to define the term strong correlation once and for all, but to highlight one possibility that is both rigorously defined and physically transparent, and remains so in reference to molecules and quantum lattice models.

Accurate force and stress calculations for solids are achieved with a neural-network wavefunction.

A detailed derivation of cumulant Green’s function methods is presented, and the performance of this scheme in describing outer-valence quasiparticle and satellite energies of molecular systems is explored.

In this contribution, the challenges associated with the long-term development of general-purpose quantum chemical software packages are discussed and illustrated with the example of the ORCA package.

We develop a spinless formulation of AC0 based on the Dyall Hamiltonian and provide a detailed comparison between AC0 and NEVPT2 approaches.

In this paper, we apply Tensor Product Selected Configuration Interaction (TPSCI) to a series of three molecular systems ranging in separability, one of which is the first application of TPSCI to an open-shell bimetallic system.

Incommensurate magnetic structure of Cu₂OCl₂, determined by a CAS + DDCI evaluation of the magnetic low energy Hamiltonian, and a Monte-Carlo determination of its ground state.

We employ Gaussian processes to more accurately and efficiently extrapolate many-body simulations to their thermodynamic limit.

Accurate electronic-structure calculations for molecules and solids with heavy elements require an interplay of electronic correlations and relativistic effects. However, this tedious task poses problems for the existing quantum chemistry machinery.

Local correlation allows accurate periodic CCSD(T) calculations to be efficiently performed for molecules on realistic surfaces with large basis sets, yielding accurate adsorption energies and vibrational frequencies.