Evert Jan Baerends

Evert Jan Baerends
Vrije Universiteit Amsterdam | VU · Department of Chemistry and Pharmaceutical Sciences

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Publications (531)
Article
Full-text available
In this paper, the history, present status, and future of density-functional theory (DFT) is informally reviewed and discussed by 70 workers in the field, including molecular scientists, materials scientists, method developers and practitioners. The format of the paper is that of a roundtable discussion, in which the participants express and exchan...
Preprint
Full-text available
In this paper, the history, present status, and future of density-functional theory (DFT) is informally reviewed and discussed by 70 workers in the field, including molecular scientists, materials scientists, method developers and practitioners. The format of the paper is that of a roundtable discussion, in which the participants express and exchan...
Article
We consider a prototypical 1D model Hamiltonian for a stretched heteronuclear molecule and construct individual components of the corresponding KS potential, namely, the kinetic, the N - 1, and the conditional potentials. These components show very special features, such as peaks and steps, in regions where the density is drastically low. Some of t...
Preprint
Full-text available
Recently we proposed an information entropy based method for electronic structure calculations within the density-matrix functional theory(DMFT) (Phys. Rev. Lett. 128, 013001), dubbed as $i$-DMFT. Comments have been raised regarding the accuracy of the one-particle density-matrix compared to that from the wave function, and the universality of the...
Preprint
Full-text available
In this paper, the history, present status, and future of density-functional theory (DFT) is informally reviewed and discussed by 70 workers in the field, including molecular scientists, materials scientists, method developers and practitioners. The format of the paper is that of a roundtable discussion, in which the participants express and exchan...
Article
Full-text available
Many references exist in the density functional theory (DFT) literature to the chemical potential of the electrons in an atom or a molecule. The origin of this notion has been the identification of the Lagrange multiplier μ = ∂E/∂N in the Euler-Lagrange variational equation for the ground state density as the chemical potential of the electrons. We...
Preprint
Full-text available
Many references exist in the density functional theory (DFT) literature to the chemical potential of the electrons in an atom or a molecule. The origin of this notion has been the identification of the Lagrange multiplier $\mu = \partial E/\partial N$ in the Euler-Lagrange variational equation for the ground state density as the chemical potential...
Preprint
We consider a prototypical 1D model Hamiltonian for a stretched heteronuclear molecule and construct individual components of the corresponding KS potential, namely: the kinetic, the N - 1, and the conditional potentials. These components show very special features, such as peaks and steps, in regions where the density is drastically low. Some of t...
Article
Full-text available
A self-consistent field method is presented within density matrix functional theory. The computational cost for a correlated many-electron calculation is reduced to that of the self-consistent-field Hartree-Fock method, while the accuracy still reaches that of sophisticated configuration interaction based methods. In this method, the two-electron c...
Article
Axial coordination to metalloporphyrins is important in many biological and catalytic processes. Experiments found the axial coordination of nitrogenous bases to nickel(II) porphyrins to be strongly favored by electron-withdrawing substituents such as perfluorophenyls at the meso carbon positions. Careful analysis of the electronic structure reveal...
Article
Full-text available
Negative ions are not accurately represented in density functional approximations (DFAs) such as (semi-)local density functionals (LDA or GGA or meta-GGA). This is caused by the much too high orbital energies (not negative enough) with these DFAs compared to the exact Kohn-Sham values. Negative ions very often have positive DFA HOMO energies, hence...
Preprint
Full-text available
The relation between the derivative of the energy with respect to occupation number and the orbital energy, $\partial E/\partial n_i = \epsilon_i$, was first introduced by Slater for approximate total energy expressions such as Hartree-Fock and exchange-only LDA, and his derivation holds for hybrid functionals as well. We argue that Janak's extensi...
Article
Full-text available
The relation between the derivative of the energy with respect to occupation number and the orbital energy, ∂E/∂ni=ϵi, was first introduced by Slater for approximate total energy expressions such as Hartree–Fock and exchange-only LDA, and his derivation holds also for hybrid functionals. We argue that Janak's extension of this relation to (exact) K...
Article
The relation of Kohn-Sham (KS) orbital energies to ionization energies and electron affinities is different in molecules and solids. In molecules, the local density approximation (LDA) and generalized gradient approximations (GGA) approximate the exact ionization energy (I) and affinity (A) rather well with self-consistently calculated (total energ...
Article
Full-text available
It is known that the asymptotic decay of the electron density outside a molecule is informative about its first ionization potential. It has recently become clear that the special circumstance that the Kohn-Sham (KS) highest-occupied molecular orbital (HOMO) has a nodal plane that extends to infinity may give rise to different cases for the asympto...
Preprint
It is known that the asymptotic decay of the electron density outside a molecule is informative about its first ionization potential. It has recently become clear that the special circumstance that the Kohn-Sham (KS) highest-occupied molecular orbital (HOMO) has a nodal plane that extends to infinity may give rise to different cases for the asympto...
Article
Almost all functionals that are currently used in density matrix functional theory have been created by some a priori ansatz that generates approximations to the second-order reduced density matrix (2RDM). In this paper, a more consistent approach is used: we analyze the 2RDMs (in the natural orbital basis) of rather accurate multi-reference config...
Article
In this paper, the history, present status, and future of density-functional theory (DFT) is informally reviewed and discussed by 70 workers in the field, including molecular scientists, materials scientists, method developers and practitioners. The format of the paper is that of a roundtable discussion, in which the participants express and exchan...
Article
It is often stated that the Kohn-Sham occupied-unoccupied gap in both molecules and solids is ``wrong". We argue that this is not a correct statement. The KS theory does not allow to interpret the exact KS HOMO-LUMO gap as the fundamental gap (difference $(I-A)$ of electron affinity ($A$) and ionization energy ($I$), twice the chemical hardness), f...
Article
We use density functional theory (DFT) and ab initio molecular dynamics to study the conversion of H2O into H2O2 in water solution by the FeIVO²⁺ group under room-temperature and -pressure conditions. We compute the free energy of formation of an O(water)–O(oxo) bond using thermodynamic integration with explicit solvent and we examine the subsequen...
Article
Straightforward interpretation of excitations is possible if they can be described as simple single orbital-to-orbital (or double, etc.) transitions. In linear response time-dependent density functional theory (LR-TDDFT), the (ground state) Kohn-Sham orbitals prove to be such an orbital basis. In contrast, in a basis of natural orbitals (NOs) or Ha...
Article
Full-text available
In spite of the high quality of exchange-correlation energies Exc obtained with the generalized gradient approximations (GGAs) of density functional theory, their xc potentials vxc are strongly deficient, yielding upshifts of ca. 5 eV in the orbital energy spectrum (in the order of 50% of high-lying valence orbital energies). The GGAs share this d...
Article
Although time-dependent density functional theory (TDDFT) has become the tool of choice for real-time propagation of the electron density ρ(N)(t) of N-electron systems, it also encounters problems in this application. The first problem is the neglect of memory effects stemming from the, in TDDFT virtually unavoidable, adiabatic approximation, the s...
Article
We analyze with DFT calculations the charge effects on the reactivity of the polycationic Compound I (Cpd I) and Compound II (Cpd II) mimics experimentally investigated by Bell and Groves (Bell, S. R.; Groves, J. T. J. Am. Chem. Soc.2009, 131, 9640). Specifically, we consider the Cpd I model [(4-THPyP)•+(H2O)FeIV═O]5+ (THPyP = 5,10,15,20-tetrakis(N...
Article
Full-text available
It is known that the asymptotic decay of the electron density $n(\br)$ outside a molecule is informative about its first ionization potential $I_0$, $n(|\br|\to\infty) \sim \text{exp}(-2\sqrt{2I_0}\,r)$. This dictates the orbital energy of the highest occupied Kohn-Sham (KS) molecular orbital (HOMO) to be $\epsilon_H=-I_0$, if the KS potential goes...
Article
Linear response density matrix functional theory has been shown to solve the main problems of time-dependent density functional theory (deficient in case of double, charge transfer and bond breaking excitations). However, the natural orbitals preclude the description of excitations as (approximately) simple orbital-to-orbital transitions: many weak...
Article
Full-text available
Water oxidation by Ti(OH)4 in the ground and excited states was investigated using density functional (∆SCF, TDDFT) methods gauged by the coupled cluster (CCSD, CCSD(T)) calculations. O2 and H2 are generated in a reaction sequence that starts with Ti(OH)4 reacting with H2O. This reaction can proceed by either nucleophilic attack by H2O or by H-atom...
Article
π-electron conjugation and aromaticity are commonly associated with delocalization and especially high mobility of the π electrons. We investigate if also the electron correlation (pair density) exhibits signatures of the special electronic structure of conjugated systems. To that end the shape and extent of the pair density and derived quantities...
Article
The electronic structure explanation of H abstraction from aliphatic CH bonds by the ferryl ion, FeIVO2+, has received a great deal of attention. We review the insights that have been gained, in particular into the effect of the spin state. However, we emphasize that the spin state is dictated by the field of the ligands coordinated to the Fe ion a...
Article
In recent years, several benchmark studies on the performance of large sets of functionals in time-dependent density functional theory (TDDFT) calculations of excitation energies have been performed. The tested functionals do not approximate exact Kohn-Sham orbitals and orbital energies closely. We highlight the advantages of (close to) exact Kohn-...
Data
Physical Meaning of Virtual Kohn–Sham Orbitals and Orbital Energies: An Ideal Basis for the Description of Molecular Excitations Tables with the calculated excitation energies for the 11 molecules for which the same excitations have been calculated as in refs 6 and 9.
Article
For chemistry an accurate description of bond weakening and breaking is vital. The great advantage of density matrix functionals, as opposed to density functionals, is their ability to describe such processes since they naturally cover both nondynamical and dynamical correlation. This is obvious in the Löwdin-Shull functional, the exact natural orb...
Article
Using the 6,6'-dibromo-[1,1'-binaphthalene]-2,2'-diol molecule and its VA and VCD spectra measured in deuterated dimethyl sulfoxide as example, we present a first detailed study of the effects induced in VCD spectra by the large-amplitude motions of solvent molecules loosely bound to a solute molecule. We show that this type of perturbation can ind...
Article
Enantiomeric excess (ee) in asymmetric catalysis may be strongly dependent on the solvent. The reaction product may range from an almost racemic mixture to an ee of over 90% for different solvents. We study this phenomenon for the C-C coupling reaction between nitromethane and benzaldehyde (the Henry reaction) with cinchona thiourea as the catalyst...
Article
Time dependent density matrix functional theory in its adiabatic linear response formulation delivers exact excitation energies ωα and oscillator strengths fα for two-electron systems if extended to the so-called phase including natural orbital (PINO) theory. The Löwdin-Shull expression for the energy of two-electron systems in terms of the natural...
Article
The basis set superposition effect (BSSE) is a simple concept, and its validity is almost universally accepted. So is the counterpoise method to correct for it. The idea is that the basis set is biased toward the dimer because each monomer in the dimer can “use” the basis functions on the other monomer, which it cannot in a simple monomer calculati...
Article
Full-text available
A number of consequences of the presence of the exchange-correlation hole potential in the Kohn-Sham potential are elucidated. One consequence is that the HOMO-LUMO orbital energy difference in the KS-DFT model (the KS gap) is not "underestimated" or even "wrong", but that it is physically expected to be an approximation to the excitation energy if...
Article
Solvation effects on chemical reactivity are often rationalised using electrostatic considerations: the reduced stabilisation of the transition state results in higher reaction barriers and lower reactivity in solution. We demonstrate that the effect of solvation on the relative energies of the frontier orbitals is equally important, and may even r...
Article
This paper gives a natural orbital (NO) based analysis of the van der Waals interaction in (singlet) H2 at long distance. The van der Waals interaction, even if not leading to a distinct van der Waals well, affects the shape of the interaction potential in the van der Waals distance range of 5-9 bohrs and can be clearly distinguished from chemical...
Article
Full-text available
The key characteristics of electronic excitations of many-electron systems, the excitation energies ωα and the oscillator strengths fα, can be obtained from linear response theory. In one-electron models and within the adiabatic approximation, the zeros of the inverse response matrix, which occur at the excitation energies, can be obtained from a s...
Article
We investigate basis set convergence for a series of density functional theory (DFT) functionals (both hybrid and nonhybrid) and compare to coupled-cluster with single and double excitations and perturbative triples [CCSD(T)] benchmark calculations. The case studied is the energetics of the water oxidation reaction by an iridium-oxo complex. Comple...
Article
Whereas a density functional that incorporates dispersion interaction has remained elusive to date, we demonstrate that in principle the dispersion energy can be obtained from a density matrix functional. In density matrix functional theory one tries to find suitable approximations to the two-particle reduced density matrix (2RDM) in terms of natur...
Article
We present a combined experimental and computational investigation of the vibrational absorption (VA) and vibrational circular dichroism (VCD) spectra of [1,1'-binaphthalene]-2,2'-diol. First, the sensitive dependence of the experimental VA and VCD spectra on the solvent is demonstrated by comparing the experimental spectra measured in CH(2)Cl(2),...
Article
Full-text available
We study the adsorption of hydrogen molecules on a titanium atom supported by a benzene molecule using generalized gradient corrected Density Functional Theory (DFT). This simple system is found to bear important analogies with titanium adsorption sites in (8, 0) titanium-coated single-walled carbon nanotubes (SWNTs) (T. Yildirim and S. Ciraci, 200...
Article
Full-text available
Adiabatic response time-dependent density functional theory (TDDFT) suffers from the restriction to basically an occupied → virtual single excitation formulation. Adiabatic time-dependent density matrix functional theory allows to break away from this restriction. Problematic excitations for TDDFT, viz. bonding-antibonding, double, charge transfer,...
Article
We study systematically the vibrational circular dichroism (VCD) spectra of the conformers of a simple chiral molecule, with one chiral carbon and an "achiral" alkyl substituent of varying length. The vibrational modes can be divided into a group involving the chiral center and its direct neighbors and the modes of the achiral substituent. Conforma...
Chapter
Full-text available
In this chapter we will give an introduction into one-body reduced density matrix functional theory (RDMFT). This is a rather new method to deal with the quantum many-body problem. Especially the development of a time-dependent version, TDRDMFT , is very recent. Therefore, there are many open questions and the formalism has not crystalized yet into...
Article
Hydroxylation of aliphatic C-H bonds is a chemically and biologically important reaction, which is catalyzed by the oxidoiron group FeO(2+) in both mononuclear (heme and nonheme) and dinuclear complexes. We investigate the similarities and dissimilarities of the action of the FeO(2+) group in these two configurations, using the Fenton-type reagent...
Article
In the oxidation of alcohols with TEMPO as catalyst, the substrate has alternatively been postulated to be oxidized but uncoordinated TEMPO(+) (Semmelhack) or Cu-coordinated TEMPO(•) radical (Sheldon). The reaction with the Cu(bipy)(2+)/TEMPO cocatalyst system has recently been claimed, on the basis of DFT calculations, to not be a radical reaction...
Article
This article investigates the errors in supermolecule calculations for the helium dimer. In a full CI calculation, there are two errors. One is the basis set superposition error (BSSE), the other is the basis set convergence error (BSCE). Both of the errors arise from the incompleteness of the basis set. These two errors make opposite contributions...
Article
Full-text available
It is known that the asymptotic decay $(r \to \infty)$ of the electron density $n(r)$ outside a molecule is informative about its first ionization potential I_0$. Contrary to conventional wisdom, we demonstrate that this asymptotic decay may not be the same in every direction. When the highest occupied Kohn-Sham molecular orbital has a nodal plane,...
Article
We study the generation of a dinuclear Fe(IV)oxo species, [EDTAH·FeO·OFe·EDTAH](2-), in aqueous solution at room temperature using Density Functional Theory (DFT) and Ab Initio Molecular Dynamics (AIMD). This species has been postulated as an intermediate in the multi-step mechanism of autoxidation of Fe(II) to Fe(III) in the presence of atmospheri...
Article
We demonstrate and advocate the use of observable quantities derived from the two-electron reduced density matrix - pair densities, conditional densities, and exchange-correlation holes--as signatures of the type of electron correlation in a chemical bond. The prototype cases of the lowest (1)Σ(u)(+) and (1)Σ(g)(+) states of H(2), which exhibit lar...
Article
The concept of robustness of rotational strengths of vibrational modes in a VCD spectrum has been introduced as an aid in assignment of the absolute configuration with the help of the VCD spectrum. The criteria for robustness have been based on the distribution around 90° of the angles ξ(i) between electric and magnetic transition dipoles of all th...
Article
We present a combined experimental and theoretical study of the diffraction of H(2) from Ru(0001) in the incident energy range 78-150 meV, and a theoretical study of dissociative chemisorption of H(2) in the same system. Pronounced out-of-plane diffraction was observed in the whole energy range studied. The energy dependence of the elastic diffract...
Article
We study the effect of counter-ion complexation on the example of Cl(-) ions interacting with the [Co(en)(3)](3+) complex. The H-bonding of the N-H groups of the ethylenediamine (en) ligands with the Cl(-) ions may lead to giant enhancement of the VCD intensity for the N-H stretches, but may also lead to VCD sign changes in the finger print region...
Article
Full-text available
The adiabatic approximation is problematic in time-dependent density matrix functional theory. With pure density matrix functionals (invariant under phase change of the natural orbitals) it leads to lack of response in the occupation numbers, hence wrong frequency dependent responses, in particular α(ω→0)≠α(0) (the static polarizability). We propos...
Article
The strength of the CN/CN′ bond decreases in the series NC-CN (1), CN-CN (2), and CN-NC (3), while simultaneously it shortens. The explanation requires that, apart from the σ pair bond between the CN 5σ MO's, the following effects be taken into account: (a) Pauli repulsion ("steric hindrance") between the 4σ ("N lone pair") orbitals; (b) Pauli repu...
Article
Full-text available
We use the natural orbitals to define an independent particle system, from which the exact one-particle density matrix can be obtained with an ensemble of degenerate determinantal ground states. Also defining explicit phases for the orbitals, and admitting functionals that are dependent on those phases, time-dependent equations for the orbitals and...
Article
The Coulomb hole does not have its largest depth around an electron in or near the bond midplane. It splits into two parts, localized on both nuclear sites forming the bond. Even counterintuitive positive values of the "hole" around such a position may be observed. This happens when the Fermi hole is deeper than the total exchange-correlation hole...
Article
Full-text available
In the major independent particle models of electronic structure theory-Hartree-Fock, Kohn-Sham (KS), and natural orbital (NO) theories-occupations are constrained to 0 and 1 or to the interval [0,1]. We carry out a constrained optimization of the orbitals and occupation numbers with application of the usual equality constraints summation (i) (infi...
Article
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Article
The known tetrathiometalates MoS42-/3-, WS42-/2-/3, ReS4-/2-/3, and the unknown species TcS4-/2-, RuS40/-, and OsS40/-/2- were calculated using ab initio and DFT methods. The one-electron reduced species with d1 configuration were shown to exhibit a slight Jahn-Teller distortion (Td → D2d); the largest corresponding stabilization energy was obtaine...
Article
Arguments are put forward that the active alpha-oxygen site in the Fe-ZSM-5 catalyst consists of the FeO(2+) moiety. It is demonstrated that this zeolite site for FeO(2+) indeed obeys the design principles for high reactivity of the FeO(2+) moiety proposed earlier: a ligand environment consisting of weak equatorial donors (rather oxygen based than...
Article
Full-text available
Electronic structure data and analytical representations of the potential energy surface for the adsorption of carbon monoxide on a crystalline copper Cu(100) substrate are reviewed. It is found that a previously published and widely used analytical hypersurface for this process [J. C. Tully, M. Gomez, and M. Head-Gordon, J. Vac. Sci. Technol. A 11...
Article
Evert Jan Baerends és catedràtic de la Universitat Lliure d’Amsterdam i de la Universitat de Ciència i Tecnologia de Pohang de Corea del Sud. És un dels impulsors de l’Amsterdam Density Functional Program System, la teoria que ha revolucionat el camp de la química teòrica i computacional moderna. La importància de la densitat electrònica es va fer...
Article
We have investigated the reaction mechanism of the selective aerobic oxidation of primary alcohols into aldehydes using a bipy-copper complex and the 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) radical as cocatalysts (Gamez et al. Chem. Commun. 2003, 2412-2415) and compared it to the well-known oxidation by the TEMPO(+) ion. Our theoretical invest...
Article
We study the cleavage of O2 in gas phase [(EDTAH)Fe(O2)Fe(EDTAH)]2-, a proposed intermediate in the aqueous Fe(II)-to-Fe(III) autoxidation reaction in the presence of atmospheric dioxygen and EDTA ligand. The role of the exchange coupling between the locally high-spin Fe centers in the O-O dissociation is investigated. Using results from broken sym...
Article
Herein we report density functional calculations of homolytic and heterolytic dissociation energies of the diatomic alkalimetal halides MX (M=Li, Na, K, Rb, and Cs and X=F, Cl, Br, I, and At) and their corresponding microsolvated structures MX(H(2)O)(n) (n=1 to 4). Our results show that the homolytic dissociation energy of the MX(H(2)O)(n) species...
Article
Full-text available
An analog of Koopmans theorem is formulated for the energies, a, of virtual KohnSham (KS) molecular orbitals (MOs) from the requirement that the KS theory provides, in principle, not only the exact electron density, but also its exact response. The starting point is the KohnSham analog of Koopmans theorem, relating the vertical ionization energies,...
Article
The use of calculations of the rotational strengths of normal modes in order to determine the absolute configuration (AC) of a molecule, by comparing a calculated vibrational circular dichroism (VCD) spectrum to an experimental one, can be made much more reliable when the vibrational modes are classified as either robust or non-robust. The robust m...
Article
Time-dependent density functional (response) theory (TDDF(R)T) is applied almost exclusively in its adiabatic approximation (ATDDFT), which is restricted to predominantly single electronic excitations and neglects additional roots of the TDDFT eigenvalue problem stemming from the interaction between single and double excitations. We incorporate the...
Article
In the search for novel hydrogen storage media, the III-V hydridic material [NH4][BH4] is a natural candidate. It can store a high wt % of hydrogen and has a favorable volumetric density. Unfortunately it was found to decompose slowly at room temperature. It is of interest to consider chemically related materials, such as the series of [XH4][YH4] i...
Article
Donor-acceptor interactions such as the one between the Cl(-) base and the N-H sigma* acceptor orbitals encountered in the complexation of Cl(-) counterions to the [Co(en)(3)](3+) transition metal complex, have been shown to cause huge enhancement (between 1 and 2 orders of magnitude) of the VCD intensities of N-H stretching modes. This effect has...
Article
Metaloxo species are often postulated as key active species in oxidative catalysis. Among all, the quintet FeO2+ moiety is particularly widespread and active: aliphatic C-H bonds undergo hydroxylation easily through a H-abstraction/O-rebound mechanism. The high electrophilicity of quintet FeO2+ originates from its electronic structure: a low lying...
Article
Full-text available
Time-dependent density functional theory in its current adiabatic implementations exhibits three striking failures: (a) Totally wrong behavior of the excited state surface along a bond-breaking coordinate, (b) lack of doubly excited configurations, affecting again excited state surfaces, and (c) much too low charge transfer excitation energies. We...
Article
The LCAO Hartree-Fock-Slater method is evaluated by comparing results of this method obtained in an accurate STO basis for a series of small diatomic molecules with experimental data and with results of Hartree-Fock calculations. It is found that the X potential, if applied with the same care as the Hartree-Fock potential (i.e., comparable basis se...
Article
The ferryl species (oxidoiron(IV), FeO(2+)) is a ubiquitous, highly oxidative intermediate in oxidation catalysis. We study theoretically its abiotic generation, in the form of the singularly active complex of FeO(2+) with the EDTAH(n)(-4+n), n = 0-4 ligands, from O(2) and Fe(2+)-EDTA complexes. The calculations are for the gas phase using generali...
Article
Vibrational modes in an achiral molecule may acquire rotational strength by complexation to a chiral molecule, as happens for achiral solvent molecules complexed to a chiral solute. We investigate this transfer of chirality in vibrational circular dichroism for the pulegone molecule in CDCl(3) solvent from the point of view of the robustness concep...
Article
A recently proposed series of corrections to the earliest JK-only functionals has considerably improved the prospects of density matrix functional theory (DMFT). Still, the most advanced of these functionals (correction C3) requires a preselection of the terms in the pair density Gamma(r(1),r(2)) involving the bonding and antibonding natural orbita...
Article
Full-text available
Adiabatic time-dependent density functional theory (ATDDFT) has much too low excitation energies at long bond length in (dissociating) electron pair bonds. This easily escapes attention partly due to the occurrence of the problems at slightly longer distances than the equilibrium geometry, and partly due to fortuitous error cancellation between wro...
Article
Full-text available
Time-dependent density functional theory (TDDFT) in its current adiabatic implementations exhibits three remarkable failures: (a) completely wrong behavior of the excited state surface along a bond-breaking coordinate; (b) lack of doubly excited configurations; (c) much too low charge transfer excitation energies. These TDDFT failure cases are all...
Article
The determination of absolute configurations of chiral compounds using VCD is performed by comparing measured vibrational circular dichroism (VCD) spectra with calculated spectra. The process is based on two facts: the two enantiomers have rotational strengths of opposite sign, and the absolute configuration of the molecule used in the calculation...
Article
The method developed recently for prediction of 1s electron spectra is now extended to the 2p spectra of SiH4, PH3, H2S, HCl, and Ar. The method for X-ray absorption spectra involves the use of DeltaE for the excitation and ionization energies, and application of time-dependent density functional theory using the exchange-correlation potential know...
Article
Full-text available
Results of experimental studies, and theoretical calculations utilizing classical trajectories, have shown that dissociation of H2 on the Pt(211) stepped surface is enhanced at low energies by a molecular trapping mechanism. Because quantum effects can play a large role at the low energies and long lifetimes that characterize molecular trapping, we...
Article
A prerequisite for the high activity of the FeO2+ moiety as a hydroxylation agent is that its ligand environment stabilizes the 3σ*LUMO, which dominates the reactivity of this system. Features in the ligand environment that promote the reactivity of FeO2+ are: weak equatorial ligand field to obtain a quintet ground state that stabilizes the unoccup...
Article
Full-text available
We have theoretically analyzed mimics of Watson-Crick AT and GC base pairs in which N-H···O hydrogen bonds are replaced by N-H···S, using the generalized gradient approximation (GGA) of density functional theory at BP86/TZ2P level. The general effect of the above substitutions is an elongation and a slight weakening of the hydrogen bonds that hold...