Roland Lindh

Roland Lindh
Uppsala University | UU · Department of Chemistry - BMC

Ph.D.

About

306
Publications
44,614
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21,687
Citations
Additional affiliations
May 2010 - present
Uppsala University
Position
  • Professor
January 1990 - April 2010
Lund University
Position
  • Professor (Full)

Publications

Publications (306)
Article
Full-text available
This Roadmap article provides a succinct, comprehensive overview of the state of electronic structure (ES) methods and software for molecular and materials simulations. Seventeen distinct sections collect insights by 51 leading scientists in the field. Each contribution addresses the status of a particular area, as well as current challenges and an...
Article
In this work, three versions of self-consistent field/Kohn–Sham density functional theory (SCF/KS-DFT) orbital optimization are described and benchmarked. The methods are a modified version of the geometry version of the direct inversion in the iterative subspace approach (which we call r-GDIIS), the modified restricted step rational function optim...
Preprint
In this report, three versions of SCF/KS-DFT orbital optimization are described and benchmarked. The methods are a modified version of the geometry version of the direct inversion in the iterative subspace approach (which we call r-GDIIS), the modified restricted step rational function optimization method (RS-RFO), and the novel subspace gradient e...
Preprint
In this report, three versions of SCF/KS-DFT orbital optimization are described and benchmarked. The methods are a modified version of the geometry version of the direct inversion in the iterative subspace approach (which we call r-GDIIS), the modified restricted step rational function optimization method (RS-RFO), and the novel subspace gradient e...
Article
Full-text available
The light-induced ultrafast switching between molecular isomers norbornadiene and quadricyclane can reversibly store and release a substantial amount of chemical energy. Prior work observed signatures of ultrafast molecular dynamics in both isomers upon ultraviolet excitation but could not follow the electronic relaxation all the way back to the gr...
Preprint
In this report, three versions of SCF/KS-DFT orbital optimization are described and benchmarked. The methods are a modified version of the geometry version of the direct inversion in the iterative subspace approach (which we call r-GDIIS), the modified restricted step rational function optimization method (RS-RFO), and the novel subspace gradient e...
Article
Based on the work done by an electromagnetic field on an atomic or molecular electronic system, a general gauge-invariant formulation of transient absorption spectroscopy is presented within the semiclassical approximation. Avoiding multipole expansions, a computationally viable expression for the spectral response function is derived from the mini...
Preprint
Full-text available
In this report, three versions of SCF/KS-DFT orbital optimization are described and benchmarked. The methods are a modified version of the gradient type of the direct inversion in the iterative subspace approach (r-GDIIS), the modified restricted step rational function optimization method (RS-RFO), and the novel subspace gradient enhanced Kriging m...
Article
We characterize the photochemically relevant conical intersections between the lowest-lying accessible electronic excited states of the different DNA/RNA nucleobases using Cholesky decomposition-based complete active space self-consistent field (CASSCF) algorithms. We benchmark two different basis set contractions and several active spaces for each...
Article
Full-text available
The resolution‐of‐the‐identity (RI) or density fitting (DF) approximation for the electron repulsion integrals (ERIs) has become a standard component of accelerated and reduced‐scaling implementations of first‐principles Gaussian‐type orbital electronic‐structure methods. The Cholesky decomposition (CD) of the ERIs has also become increasingly depl...
Preprint
We characterise the photochemically relevant conical intersections between the lowest-lying accessible electronic excited states of the different DNA/RNA nucleobases using Cholesky decomposition-based complete active space selfconsistent field (CASSCF) algorithms. We benchmark two different basis set contractions and several active spaces for each...
Preprint
Full-text available
The resolution-of-the-identity (RI) or density fitting (DF) approximation for the electron repulsion integrals (ERIs) has become a standard component of accelerated and reduced-scaling implementations of first-principles Gaussian- type orbital electronic-structure methods. The Cholesky decomposition (CD) of the ERIs has also become increasingly dep...
Preprint
Based on the work done by an electromagnetic field on an atomic or molecular electronic system, a general gauge invariant formulation of transient absorption spectroscopy is presented within the semi-classical approximation. Avoiding multipole expansions, a computationally viable expression for the spectral response function is derived from the min...
Preprint
Full-text available
The resolution-of-the-identity (RI) or density fitting (DF) approximation for the electron repulsion integrals (ERIs) has become a standard component of accelerated and reduced-scaling implementations of first-principles Gaussian- type orbital electronic-structure methods. The Cholesky decomposition (CD) of the ERIs has also become increasingly dep...
Article
Full-text available
Cholesky decomposition (CD) of the two-electron integrals and the resolution-of-identity (RI) techniques are established inner projection methods to efficiently evaluate the two-electron integrals. Both approaches share the notion of an auxiliary basis set as a mean to reduce the scaling. In the past years, the close relationship between the two...
Article
The developments of the open-source OpenMolcas chemistry software environment since spring 2020 are described, with a focus on novel functionalities accessible in the stable branch of the package or via interfaces with other packages. These developments span a wide range of topics in computational chemistry and are presented in thematic sections: e...
Article
The optimization of conical intersection structures is complicated by the nondifferentiability of the adiabatic potential energy surfaces. In this work, we build a pseudodiabatic surrogate model, based on Gaussian process regression, formed by three smooth and differentiable surfaces that can adequately reproduce the adiabatic surfaces. Using this...
Preprint
Full-text available
This chapter presents the theory behind the CASPT2 method and its adaptation to a multi-state formalism. The chapter starts with an introduction of the theory of the CASPT2 method - an application of Rayleigh-Schr\"odinger perturbation theory applied to multiconfigurational reference function - as it was originally presented. In particular, we disc...
Preprint
Full-text available
Over the past three decades, the resolution-of-the-identity (RI) approximation of electron repulsion integrals (ERIs) over Gaussian-type orbitals has become a stan- dard component of accelerated and reduced-scaling implementations of first-principles electronic-structure methods. For the first two decades, the closely related approach based on Chol...
Preprint
The optimization of conical intersection structures is complicated by the non-differentiability of the adiabatic potential energy surfaces. In this work, we build a pseudo-diabatic surrogate model, based on Gaussian process regression, formed by three smooth and differentiable surfaces that can adequately reproduce the adiabatic surfaces. Using thi...
Preprint
Full-text available
In this article the recent developments of the open-source OpenMolcas chemistry software environment, since spring 2020, are described, with the main focus on novel functionalities that are accessible in the stable branch of the package and/or via interfaces with other packages. These community developments span a wide range of topics in computatio...
Preprint
Full-text available
Cholesky decomposition (CD) of the two-electron integrals and the resolution-of-identity (RI) techniques are established inner projection methods to efficiently evaluate the two-electron integrals. Both approaches share the notion of an auxiliary basis set as a mean to reduce the scaling. In the past years, the close relationship between the two ap...
Preprint
Full-text available
The optimization of conical intersection structures is complicated by the non-differentiability of the adiabatic potential energy surfaces. In this work, we build a pseudo-diabatic surrogate model, based on Gaussian process regression, formed by three smooth and differentiable surfaces that can adequately reproduce the adiabatic surfaces. Using thi...
Preprint
Full-text available
In this article the recent developments of the open-source OpenMolcas chemistry software environment, since spring 2020, are described, with the main focus on novel functionalities that are accessible in the stable branch of the package and/or via interfaces with other packages. These community developments span a wide range of topics in computatio...
Chapter
Molecular structure optimization is one of the most common tasks performed in computational chemistry. Many applications require locating special points in a potential energy surface: minima, saddle points, and others. Given that the calculation of energies and gradients with accurate quantum chemical methods is quite computationally demanding, one...
Article
Conformational analysis is central to the design of bioactive molecules. It is particularly challenging for macrocycles due to noncovalent transannular interactions, steric interactions, and ring strain that are often coupled. Herein, we simulated the conformations of five macrocycles designed to express a progression of increasing complexity in en...
Article
Photochemical reactions often involve states that are closely coupled due to near degeneracies, for example by proximity to conical intersections. Therefore, a multistate method is used to accurately describe these states; for example, ordinary perturbation theory is replaced by quasidegenerate perturbation theory. Multiconfiguration pair-density f...
Article
Full-text available
In this work we present a new approach to fix the intruder-state problem (ISP) in CASPT2 based on σp regularization. The resulting σp-CASPT2 method is compared to previous techniques, namely, the real and imaginary level shifts, on a theoretical basis and by performing a series of systematic calculations. The analysis is focused on two aspects, the...
Preprint
Full-text available
In this work we present a new approach to fix the intruder state problem (ISP) in CASPT2 based on σp regularization. The resulting $σ^p$-CASPT2 method is compared to previous techniques, namely the real and imaginary level shifts, on a theoretical basis and by performing a series of systematic calculations. The analysis is focused on two aspects, t...
Article
Crossings between states involve complex electronic structures, making the accurate characterization of the crossing point difficult. In this study, the analytic derivatives of three complete active space second-order perturbation theory (CASPT2) variants as well as an extension of the restricted active space (RASPT2) are developed. These variants...
Preprint
Full-text available
In the future, computer-supported molecular design will be the rule rather than the exception. Conformational analysis is central to design, but is particularly challenging for macrocycles due to noncovalent transannular interactions, steric interactions, and ring strain that are often coupled. In this report, six simulation protocols are verified...
Preprint
Full-text available
Crossings between states involve complex electronic structures, making the accurate characterization of the crossing point difficult. In this study, the analytic derivatives of three complete active space second-order perturbation theory (CASPT2) variants as well as an extension of the restricted active space (RASPT2) are developed. These variants...
Preprint
Full-text available
In this work we present a new approach to fix the intruder state problem (ISP) in CASPT2 based on σp regularization. The resulting $σ^p$-CASPT2 method is compared to previous techniques, namely the real and imaginary level shifts, on a theoretical basis and by performing a series of systematic calculations. The analysis is focused on two aspects, t...
Article
Full-text available
The interaction of a [bis(pyridine)iodine(I)] ⁺ cation with a [bis(pyridine)silver(I)] ⁺ cation, in which an iodonium ion acts as nucleophile by transferring electron density to the silver(I) cation, is reinvestigated herein. No...
Preprint
Full-text available
Crossings between states involve complex electronic structures, making the accurate characterization of the crossing point difficult. In this study, the analytic derivatives of three complete active space second-order perturbation theory (CASPT2) variants as well as an extension of the restricted active space are developed. These variants are appli...
Article
Density fitting reduces the computational cost of both energy and gradient calculations by avoiding the computation and manipulation of four-index electron repulsion integrals. With this algorithm, one can efficiently optimize the geometries of large systems with an accurate multireference treatment. Here, we present the derivation of multiconfigur...
Article
Full-text available
Herewith, we propose two new exponents for the recently introduced XDW-CASPT2 method [S. Battaglia and R. Lindh, J. Chem. Theory Comput. 16, 1555–1567 (2020)], which fix one of the largest issues hindering this approach. By using the first-order effective Hamiltonian coupling elements, the weighting scheme implicitly takes into account the symmetry...
Article
Full-text available
Gaussian process regression has recently been explored as an alternative to standard surrogate models in molecular equilibrium geometry optimization. In particular, the gradient-enhanced Kriging approach in association with internal coordinates, restricted-variance optimization, and an efficient and fast estimate of hyperparameters has demonstrated...
Chapter
The purpose of the present chapter is to give students a detailed introduction to time‐independent multi‐configurational reference perturbation theory (MRPT), in particular the CASPT2 method, one of the standard tools for the study of excited states of molecular systems of small to intermediate size. To achieve this, in as closed a form as possible...
Chapter
This chapter describes what electronic excited states are and why they are important to study and therefore motivates the need for theoretical tools able to characterize them. Further and most importantly, in this introductory chapter, we put together in a comprehensive manner a collection of basic concepts that might be needed, depending on the ba...
Article
Full-text available
Gold(III) complexes are versatile catalysts offering a growing number of new synthetic transformations. Our current understanding of the mechanism of homogeneous gold(III) catalysis is, however, limited, with that of phosphorus-containing complexes being hitherto underexplored. The ease of phosphorus oxidation by gold(III) has so far hindered the u...
Preprint
Gaussian process regression has recently been explored as an alternative to standard surrogate models in molecular equilibrium geometry optimization. In particular, the gradient-enhanced Kriging approach in association with internal coordinates, restricted-variance optimization, and an efficient and fast estimate of hyperparameters have demonstrate...
Article
Full-text available
Because of their anisotropic electron distribution and electron deficiency, halonium ions are unusually strong halogen-bond donors that form strong and directional three-center, four-electron halogen bonds. These halogen bonds have received considerable attention owing to their applicability in supramolecular and synthetic chemistry and have been i...
Article
Full-text available
Dinoflagellates are the dominant source of bioluminescence in coastal waters. The luminescence reaction involves the oxidation of luciferin by a luciferase enzyme, which only takes place at low pH. The pH-dependence has previously been linked to four conserved histidines. It has been suggested that their protonation might induce a conformational ch...
Article
Full-text available
X-ray processes involve interactions with high-energy photons. For these short wavelengths, the perturbing field cannot be treated as constant, and there is a need to go beyond the electric-dipole approximation. The exact semi-classical light–matter interaction operator offers several advantages compared to the multipole expansion such as improved...
Article
Full-text available
Three-center, four-electron bonds provide unusually strong interactions; however, their nature remains ununderstood. Investigations of the strength, symmetry and the covalent versus electrostatic character of three-center hydrogen bonds have vastly contributed to the understanding of chemical bonding, whereas the assessments of the analogous three-...
Article
Full-text available
MOLCAS/OpenMolcas is an ab initio electronic structure program providing a large set of computational methods from Hartree–Fock and density functional theory to various implementations of multiconfigurational theory. This article provides a comprehensive overview of the main features of the code, specifically reviewing the use of the code in previo...
Article
Full-text available
Benzene exhibits a rich photochemistry which can provide access to complex molecular scaffolds difficult to access with reactions in the electronic ground state. While benzene is aromatic in its ground state it is antiaromatic in its lowest ππ* excited states. Herein, we clarify to what extent relief of excited state antiaromaticity (ESAA) triggers...
Article
Full-text available
Machine learning techniques, specifically gradient-enhanced Kriging (GEK), have been implemented for molecular geometry optimization. GEK-based optimization has many advantages compared to conventional – step-restricted second-order truncated expansion – molecular optimization methods. In particular, the surrogate model given by GEK can have multip...
Article
Theoretical simulations are frequently used to assign electronic and geometric structure from spectral fingerprints. However, such assignments are prone to expectation bias. Bias can be reduced by using numerical measures of the similarity between calculated and experimental spectra. However, the commonly used point-wise comparisons cannot handle l...
Article
Full-text available
Hard X-ray spectroscopy selectively probes metal sites in complex environments. Resonant inelastic X-ray scattering (RIXS) makes it is possible to directly study metal-ligand interactions through local valence excitations. Here multiconfigurational wavefunction simulations are used to model valence K pre-edge RIXS for three metal-hexacyanide comple...
Preprint
Machine learning techniques, specifically Gradient-Enhanced Kriging (GEK), has been implemented for molecular geometry optimization. GEK has many advantages as compared to conventional -- step-restricted second-order truncated -- molecular optimization methods. In particular, the surrogate model associated with GEK can have multiple stationary poin...
Article
Predicting and understanding the chemical bond is one of the major challenges of computational quantum chemistry. Kohn−Sham density functional theory (KS-DFT) is the most common method, but approximate density functionals may not be able to describe systems where multiple electronic configurations are equally important. Multiconfigurational wave fu...
Article
Full-text available
In this paper, we examine decay and fragmentation of core-excited and core-ionized water molecules combining quantum chemical calculations and electron-energy-resolved electron–ion coincidence spectroscopy. The experimental technique allows us to connect electronic decay from core-excited states, electronic transitions between ionic states, and dis...
Article
Full-text available
We introduce a new variant of the complete active space second-order perturbation theory (CASPT2) method that performs similarly to multistate CASPT2 (MS-CASPT2) in regions of the potential energy surface where the electronic states are energetically well separated and is akin to extended MS-CASPT2 (XMS-CASPT2) in case the underlying zeroth-order r...
Article
Full-text available
Post-calculation analyses are often required to extract physical insights from ab initio molecular dynamics simulations. In the present work, we use different machine learning classifiers to take a new perspective on the decomposition reaction of dioxetane. Upon thermally activated decomposition, dioxetane can form products in an electronically exc...
Preprint
div>Predicting and understanding the chemical bond is one of the major challenges of computational quantum chemistry. Kohn−Sham density functional theory (KS-DFT) is the most common method, but approximate density functionals may not be able to describe systems where multiple electronic configurations are equally important. Multiconfigurational wav...
Preprint
We introduce a new variant of the complete active space second-order perturbation theory (CASPT2) method that performs similarly to multistate CASPT2 (MS-CASPT2) in regions of the potential energy surface where the electronic states are energetically well separated and is akin to extended MS-CASPT2 (XMS-CASPT2) in case the underlying zeroth-order r...
Article
In this article we describe the OpenMolcas environment and invite the computational chemistry community to collaborate. The open-source project already includes a large number of new developments realized during the transition from the commercial MOLCAS product to the open-source platform. The paper initially describes the technical details of the...
Preprint
In this article we describe the OpenMolcas environment and invite the computational chemistry community to collaborate. The open-source project already includes a large number of new developments realized during the transition from the commercial MOLCAS product to the open-source platform. The paper initially describes the technical details of the...
Article
We introduce two new approaches to compute near-degenerate electronic states based on the driven similarity renormalization group (DSRG) framework. The first approach is a unitary multi-state formalism based on the DSRG (MS-DSRG), whereby an effective Hamiltonian is built from a set of state-specific solutions. The second approach employs a dynamic...
Article
Full-text available
Light emission from luminol is probably one of the most popular chemiluminescence reactions due to its use in forensic science, and has recently displayed promising applications for the treatment of cancer in deep tissues. The mechanism is, however, very complex and distinct possibilities have been proposed. By efficiently combining DFT and CASPT2...
Article
Quantum‐chemistry determinations of the luminol chemiluminescence mechanism have made it possible to: first, clarify the spin inversion of the reaction; secondly, to determine the concerted nature of the two steps of 3O2 addition and 1N2 elimination; thirdly, to answer why such oxygen by nitrogen substitution must occur for an efficient excited‐sta...
Article
We present an analytical and numerical solution of the calculation of the transition moments for the exact semiclassical light-matter interaction for wave functions expanded in a Gaussian basis. By a simple manipulation we show that the exact semiclassical light-matter interaction of a plane wave can be compared to a Fourier transformation of a Gau...
Article
Full-text available
Molecular dynamics simulations are often key to the understanding of the mechanism, rate and yield of chemical reactions. One current challenge is the in-depth analysis of the large amount of data produced by the simulations, in order to produce valuable insight and general trends. In the present study, we propose to employ recent machine learning...
Article
The capability of the multiconfigurational restricted active space approach to identify electronic structure from spectral fingerprints is explored by applying it to iron L-edge X-ray absorption spectroscopy (XAS) of three heme systems that represent the limiting descriptions of iron in the Fe-O2 bond, ferrous and ferric [Fe(P)(ImH)2] (P = porphine...
Preprint
Full-text available
We present an analytical and numerical solution of the calculation of the transition moments for the exact semi-classical light-matter interaction for wavefunctions expanded in a Gaussian basis. By a simple manipulation we show that the exact semi-classical light-matter interaction of a plane wave can be compared to a Fourier transformation of a Ga...
Article
In this work, we investigated muonic atoms and molecules from a quantum chemist's viewpoint by incorporating muons in the CASSCF model. With the aim of predicting muonic X‐ray energies, primitive muonic basis sets were developed for a selection of elements. The basis sets were then used in CASSCF calculations of various atoms and molecules to calcu...
Article
The bioluminescence emission from fireflies is an astounding tool to mark and view cells. However, the bioluminescent mechanism is not completely deciphered, limiting the comprehension of key processes. We use a theoretical approach to study for the first time the arrival of a dioxygen molecule inside the firefies protein and the formation of the d...
Article
Bioluminescence is a phenomenon that has fascinated mankind for centuries. Today the phenomenon and its sibling, chemiluminescence, have impacted society with a number of useful applications in fields like analytical chemistry and medicine, just to mention two. In this review, a molecular-orbital perspective is adopted to explain the chemistry behi...
Article
Full-text available
To date, the program for the development of methods and models for atomistic and continuum simulation directed toward chemicals and materials has reached an incredible degree of sophistication and maturity. Currently, one can witness an increasingly rapid emergence of advances in computing, artificial intelligence, and robotics. This drives us to c...
Article
Full-text available
Automatic Differentiation (AD) is a powerful tool that allows calculating derivatives of implemented algorithms with respect to all of their parameters up to machine precision, without the need to explicitly add any additional functions. Thus, AD has great potential in quantum chemistry, where gradients are omnipresent but also difficult to obtain,...
Preprint
Automatic Differentiation (AD) is a powerful tool that allows calculating derivatives of implemented algorithms with respect to all of their parameters up to machine precision, without the need to explicitly add any additional functions. Thus, AD has great potential in quantum chemistry, where gradients are omnipresent but also difficult to obtain,...
Article
Full-text available
Analytic gradient routines are a desirable feature for quantum mechanical methods, allowing for efficient determination of equilibrium and transition state structures and several other molecular properties. In this work, we present analytical gradients for multiconfiguration pair-density functional theory (MC-PDFT) when used with a state-specific c...