Abstract ORCA is a general‐purpose quantum chemistry program package that features virtually all modern electronic structure methods (density functional theory, many‐body perturbation and coupled cluster theories, multireference semiempirical methods). It designed with the aim of generality, extendibility, efficiency, user friendliness. Its main field application larger molecules, transition metal complexes, their spectroscopic properties. uses standard Gaussian basis functions fully...

This short update provides an overview of the capabilities that have been added to ORCA electronic structure package (version 4.0) since publication first article in 2012. WIREs Comput Mol Sci 2018, 8:e1327. doi: 10.1002/wcms.1327 is categorized under: Electronic Structure Theory > Ab Initio Methods Density Functional Software Quantum Chemistry

In this contribution to the special software-centered issue, ORCA program package is described. We start with a short historical perspective of how project began and go on discuss its current feature set. has grown into rather comprehensive general-purpose for theoretical research in all areas chemistry many neighboring disciplines such as materials sciences biochemistry. features density functional theory, range wavefunction based correlation methods, semi-empirical even force-field...

Abstract Version 5.0 of the ORCA quantum chemistry program suite was released in July 2021. represents a major improvement over all previous versions and features (1) highly improved performance, (2) increased numerical robustness, (3) host new functionality, (4) greatly user friendliness. The article describes most salient program. This is categorized under: Electronic Structure Theory > Ab Initio Methods Data Science Computer Algorithms Programming Software Quantum Chemistry

In previous publications, it was shown that an efficient local coupled cluster method with single- and double excitations can be based on the concept of pair natural orbitals (PNOs) [F. Neese, A. Hansen, D. G. Liakos, J. Chem. Phys. 131, 064103 (2009)10.1063/1.3173827]. The resulting orbital-coupled-cluster single (LPNO-CCSD) has since been proven to highly reliable efficient. For large molecules, number amplitudes determined is reduced by a factor 105–106 relative canonical CCSD calculation...

In this work, the extension of previously developed domain based local pair-natural orbital (DLPNO) singles- and doubles coupled cluster (DLPNO-CCSD) method to perturbatively include connected triple excitations is reported. The development on concept triples-natural orbitals that span joint space three pair natural (PNO) spaces electron pairs are involved in calculation a given triple-excitation contribution. truncation error very smooth can be significantly reduced through extrapolation...

A family of segmented all-electron relativistically contracted (SARC) basis sets for the elements Hf-Hg is constructed use in conjunction with Douglas-Kroll-Hess (DKH) and zeroth-order regular approximation (ZORA) scalar relativistic Hamiltonians. The SARC are loosely thus offer computational advantages compared to generally sets, while their sufficiently small size allows them be used place effective core potentials (ECPs) routine studies molecules. Practical assessments DFT calculations...

Domain based local pair natural orbital coupled cluster theory with single-, double-, and perturbative triple excitations (DLPNO-CCSD(T)) is a highly efficient correlation method. It known to be accurate robust can used in black box fashion order obtain quality total energies for large molecules several hundred atoms. While previous implementations showed near linear scaling up few atoms, nonlinear steps limited the applicability of method very systems. In this work, these limitations are...

A straightforward modification of the resolution identity (RI) approximation to Coulomb interaction is described. In limit basis sets that are dominated by high angular momentum functions observed speedups in realistic test systems reach a factor 2 compared standard RI algorithm, and up 300 algorithm form matrix. More moderate savings on order 0-20% obtained for more commonly used smaller sets. series calculations reported illustrate efficiency algorithm.

A central light atom in a cofactor at the nitrogenase active site is identified as carbon.

The “chain of spheres” (COS) algorithm, as part the RIJCOSX SCF procedure, approximates exchange term by performing analytic integration with respect to coordinates only one two electrons, whereas for remaining coordinates, is carried out numerically. In present work, we attempt enhance efficiency method minimizing numerical errors in COS procedure. main idea based on work Friesner and consists finding a fitting matrix, \documentclass[12pt]{minimal}\begin{document}$\mathbf...

Approximations to the Breit-Pauli form of spin-orbit coupling (SOC) operator are examined. The focus is on approximations that lead an effective quasi-one-electron which leads efficient property evaluations. In particular, accurate mean-field (SOMF) method developed by Hess, Marian, Wahlgren, and Gropen examined in detail. It compared detail with "effective potential" commonly used density functional theory (DFT) has been criticized for not including spin-other orbit (SOO) contribution. Both...

The domain based local pair natural orbital coupled cluster method with single-, double-, and perturbative triple excitations (DLPNO–CCSD(T)) is an efficient quantum chemical that allows for calculations on molecules hundreds of atoms. Because coupled-cluster theory the choice if high-accuracy needed, DLPNO–CCSD(T) very promising large-scale application. However, various approximations have to be introduced in order reach near linear scaling also introduce limited deviations from canonical...

In this communication, an improved perturbative triples correction (T) algorithm for domain based local pair-natural orbital singles and doubles coupled cluster (DLPNO-CCSD) theory is reported. our previous implementation, the semi-canonical approximation was used linear scaling achieved both DLPNO-CCSD parts of calculation. work, we refer to method as DLPNO-CCSD(T0) emphasize approximation. It well-established that can predict very accurate absolute relative energies with respect parent...

The calibration of two popular density functionals (B3LYP and BP86) for the prediction isomer shifts (IS) in 57Fe Mössbauer (MB) spectra is reported. A linear correlation between non-relativistically calculated theoretical electron densities experimentally measured ISs established. Both lead to accurate predictions MB with standard deviations on order approximately 0.1 mm s−1 over a range 2 s−1. holds complexes different total charge, spin, valence state at iron, coordination number...

The conductor-like screening model (COSMO) was used to investigate the solvent influence on electronic g-values of organic radicals. previously studied diphenyl nitric oxide and di-tert-butyl radicals were taken as test cases. calculations employed spin-unrestricted density functional theory BP B3LYP functionals. g-tensors calculated mixed second derivative properties with respect external magnetic field electron moment. first-order response Kohn−Sham orbitals determined through...

A production level implementation of the closed-shell local quadratic configuration interaction and coupled cluster methods with single double excitations (QCISD CCSD) based on concept pair natural orbitals [local orbital LPNO-QCISD LPNO-CCSD) is reported, evaluated, discussed. This work an extension earlier developed LPNO coupled-electron approximation (LNPO-CEPA) method [F. Neese et al., Chem. Phys. 130, 114108 (2009)] makes extended use resolution identity (RI) or density fitting (DF)...

Coupled-electron pair approximations (CEPAs) and coupled-pair functionals (CPFs) have been popular in the 1970s 1980s yielded excellent results for small molecules. Recently, interest CEPA CPF methods has renewed. It shown that these lead to competitive thermochemical, kinetic, structural predictions. They greatly surpass second order Møller–Plesset density functional theory based approaches accuracy are intermediate quality between CCSD CCSD(T) extended benchmark studies. In this work an...

A method for calculating the EPR g-tensor based on coupled perturbed Hartree–Fock (HF) and density functional theory (DFT) is presented. The one-electron molecular orbitals of a spin- unrestricted Slater determinant are calculated up to first order in applied magnetic field. evaluated as mixed second derivative property with respect field electron moment. Thus, spin-polarization spin–orbit coupling simultaneously included calculation. treatment focuses orbitally nondegenerate molecules but...

A series of two-coordinate complexes iron(II) were prepared and studied for single-molecule magnet behavior. Five the compounds, Fe[N(SiMe3)(Dipp)]2 (1), Fe[C(SiMe3)3]2 (2), Fe[N(H)Ar′]2 (3), Fe[N(H)Ar*]2 (4), Fe(OAr′)2 (5) feature a linear geometry at FeII center, while sixth compound, Fe[N(H)Ar#]2 (6), is bent with an N–Fe–N angle 140.9(2)° (Dipp = C6H3-2,6-Pri2; Ar′ C6H3-2,6-(C6H3-2,6-Pri2)2; Ar* C6H3-2,6-(C6H2-2,4,6-Pri2)2; Ar# C6H3-2,6-(C6H2-2,4,6-Me3)2). Ac magnetic susceptibility data...

A procedure was developed to automatically generate auxiliary basis sets (ABSs) for use with the resolution of identity (RI) approximation, starting from a given orbital set (OBS). The goal is provide an accurate and universal solution cases where no optimized ABSs are available. In this context, "universal" understood as ability ABS be used Coulomb, exchange, correlation energy fitting. generation scheme (denoted AutoAux) works by spanning product space OBS using even-tempered expansion...