Themed collection Fragment and localized orbital methods in electronic structure theory

New fragment and local correlation methods in electronic structure theory are providing new insights into macromolecules and the condensed phase.

Local coupled-cluster methods with pair natural orbitals and explicitly correlated terms approach the CCSD/CBS limit quickly with small domains and basis sets.

The elongation method, proposed in the early 1990s, originally for theoretical synthesis of aperiodic polymers, has been reviewed.

The procedure of the linear-scaling DC-UHF/UDFT method, which is capable of treating delocalized and/or open-shell systems.

Method development and applications of FMO to various chemical systems are reviewed.

Fragment-based electronic structure methods are creating new, computationally affordable opportunities for accurately modeling molecular crystal structures and properties.

There exists a hierarchy of methods for the calculation of electron correlation effects in solids at moderate computational costs.

CRYSCOR, an efficient periodic post Hartree–Fock program to study electron correlation in crystals from first principles.

We discovered situations where strictly integer fragment occupations arise in Partition-Density-Functional Theory. We explain why this happens, and discuss consequences.

A proof of the extensivity of energy in an electrically neutral, metallic or nonmetallic crystal.

We explore electron correlation in continuum 1d model systems, discovering similarities and differences with 3d for small atoms and molecules.

Conditions for natural fragmentation schemes are described and some aspects of their chemical relevance are discussed.

A parallelized algorithm and implementation of canonical transformation theory are presented along with a modification to the amplitude equation with inclusion of the level shift to remove the undesired intruder states.

Fragmental QM methods with Ewald summation for periodic systems.

A localized orbital-optimized coupled cluster method is applied to computations of optical rotations of chiral molecules.

A B3LYP-DBLOC empirical correction scheme has been developed for accurately and inexpensively calculating ligand removal enthalpies of transition metal complexes by systematically isolating errors in B3LYP.

An accurate description of ionized states of clusters without high expense: accurate n-electron fragment wavefunctions interact via one-electron couplings.

The cumulative dispersion energy of two isomers of water hexamers.

The interaction of a water molecule with the MgO(100) surface was studied using coupled MP2, and DFT based symmetry–adapted perturbation theory in conjunction with cluster models and diffusion Monte Carlo calculations combined with slab models and periodic boundary conditions.

We have developed an ab initio, systematically-improvable hierarchy of theoretical methods for describing intermolecular interactions in clusters in a computationally tractable way.

Linear-scaling, embedded-fragment, second-order perturbation calculations of structures, phonon dispersion, and phonon density of states of solid hydrogen fluoride under pressure.

Two new strategies are introduced to further improve the cluster-in-molecule (CIM) method for local correlation calculations of large molecules.

CO₂ clusters: the complete basis set limit of interaction energies and vibrational spectra at the MP2/aug-cc-pVDZ level of theory.

Two electronic structure methods are presented and compared with fully ab initio results for the predicted binding energies of water clusters.

This work demonstrates how the reformulated density fragment interaction approach can be applied for efficient and accurate simulations of liquid water.

DFT predictions of relative energies of organic crystal polymorphs are dramatically improved through a simple two-body correction scheme.

A statistical model is presented for quickly estimating BSSE in QM calculations of large biomolecular systems.

An efficient automated procedure for estimating the ab initio electronic energies of large molecules, such as proteins, is presented.

The electrostatically embedded many-body (EE-MB) method is extended to the calculation of dipole moments, partial atomic charges, and charge transfer.

A new local approximately size extensive multireference singles and doubles configuration interaction (MRSDCI) method is presented.

Solvent effects are included in the Automated Fragmentation QM/MM calculation of protein NMR chemical shifts. The computed proton chemical shifts represent clear improvement over that from the gas phase calculation.