E. Baerends - Academia.edu (original) (raw)
Papers by E. Baerends
Journal of Chemical Physics, Nov 15, 2000
and it is a condition of accessing publications that users recognise and abide by the legal requi... more and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Journal of Chemical Physics, May 15, 2000
and it is a condition of accessing publications that users recognise and abide by the legal requi... more and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Journal of Chemical Theory and Computation, Jul 27, 2022
Physical Chemistry Chemical Physics, 2022
Chemical Physics Letters, Dec 1, 2006
It is well known, that second-order perturbation theory (PT2) breaks down when the gap between th... more It is well known, that second-order perturbation theory (PT2) breaks down when the gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied MO (LUMO) becomes too low. It is demonstrated that when the local Kohn–Sham (KS) potential vs is approximated by an expansion in a set of basis functions, exact HOMO–LUMO degeneracy occurs, if a finite orbital
Journal of Chemical Physics, Oct 23, 2008
A recently proposed series of corrections to the earliest JK-only functionals has considerably im... more A recently proposed series of corrections to the earliest JK-only functionals has considerably improved the prospects of density matrix functional theory ͑DMFT͒. Still, the most advanced of these functionals ͑correction C3͒ requires a preselection of the terms in the pair density ⌫͑r 1 , r 2 ͒ involving the bonding and antibonding natural orbitals ͑NOs͒ belonging to an electron pair bond. Ideally, a DMFT functional should only depend on the NOs and their occupation numbers, and we propose a functional with an occupation number driven weighing of terms in the pair density. These are formulated as "damping" for certain ranges of occupation numbers of the two-electron cumulant that arises in the expansion of the two-particle density matrix of the paradigmatic two-electron system. This automatic version of C3, which we denote AC3, provides the correct dissociation limit for electron pair bonds and it excellently reproduces the potential energy curves of the multireference configuration interaction ͑MRCI͒ method for the dissociation of the electron pair bond in the series of the ten-electron hydrides CH 4 , NH 3 , H 2 O, and HF. AC3 reproduces closely the experimental equilibrium distances and at R e it yields correlation energies of the ten-electron systems with an average error in the absolute values of only 3.3% compared to the MRCI values. We stress the importance of treatment of strong correlation cases ͑NO occupation numbers differing significantly from 2.0 and 0.0͒ by appropriate terms in the cumulant.
Surface Science, May 1, 1994
ABSTRACT
Physical review, Oct 15, 1986
Journal of Molecular Structure-theochem, Apr 1, 2006
For functionals that depend on the Kohn-Sham orbitals, the optimized effective potential method (... more For functionals that depend on the Kohn-Sham orbitals, the optimized effective potential method (OEP) of density functional theory (DFT) seeks a lowest energy solution by finding that particular local potential v s for which a stationary value of the energy is obtained, dE/dv s Z0. We assess the performance of a particular method of solution, namely the expansion of v s , or the rest term v s-v 0 , in a finite set of expansion functions, using the exact exchange functional (EXX) as the simplest realistic orbital dependent functional. Here, v 0 is a fixed local potential having the longrange asymptotics K1/r. For some prototype small systems the interdependence of the basis sets for the Kohn-Sham orbitals and for the potential has been investigated, as well as the effect of the reference potential v 0. We specifically address the numerical precision with which the total energy E EXX and the orbital energies f3 EXX i g can be obtained. The EXX solution is obtained both with and without explicitly imposing the 'HOMO condition' that the energy 3 H of the highest occupied molecular orbital be equal to the expectation value of the Fock operator. The potential expansion method yields reliable total energies even without the use of a reference potential (v 0 Z0). However, the reliability of the calculated orbital energies remains a serious problem. Without the HOMO condition even the use of reference potentials with correct asymptotics cannot prevent an uncontrolled shift of the orbital energies. Imposing the HOMO condition solves this problem. But even with this condition imposed, the accuracy of other orbital energies is, typically, many orders of magnitude lower than that for the total energy.
Journal of Physical Chemistry A, Jul 1, 2003
The formation of active intermediates from the Fenton-like reagent (a mixture of iron(III) ions a... more The formation of active intermediates from the Fenton-like reagent (a mixture of iron(III) ions and hydrogen peroxide) in aqueous solution has been investigated using static DFT calculations and Car-Parrinello molecular dynamics simulations. We show the spontaneous formation of the iron(III) hydroperoxo intermediate in a first step. The Fenton-like reaction thus proceeds very differently compared to Fenton's reagent (i.e., the Fe II /H 2 O 2 mixture), for which we have recently shown that the first step is the spontaneous O-O lysis of hydrogen peroxide when coordinated to iron(II) in water. For the second step in the reaction mechanism of the Fenton-like reagent, we compare the possibilities of homolysis and heterolysis of the O-O bond and the Fe-O bond of the produced [(H 2 O) 5 Fe III OOH] 2+ intermediate. We find that concomitant hydrolysis of the reacting species plays a crucial role and, taking this into account, that O-O homolysis ([(H 2 O) 4 (OH)Fe III-OOH] + f [(H 2 O) 4 (OH)Fe IV O] + + OH •) in vacuo is a likely second step with ∆E 0k ‡) 26 kcal/mol. However, proper inclusion of the solvent effects is important, in particular, for the heterolysis reactions, in which case the large endothermicy of the charge separations can be compensated by the hydration energies from the ion solvation. In this work, we also calculate the free energy barrier for the O-O homolysis of the iron(III) hydroperoxo intermediate in aqueous solution at T) 300 K, using the method of constrained molecular dynamics and thermodynamic integration, resulting in ∆A 300K ‡) 21 kcal/mol. Analysis of the vibrational spectra of the high-spin (S) 5/2) and low-spin (S) 1/2) Fe(III)OOH intermediates confirm the, in the literature, suggested effect of the spin state on the Fe-O and O-O bond strengths. In fact, we predict that with ligands inducing a low-spin iron(III) hydroperoxo intermediate, the barrier for the O-O homolysis will be even significantly lower.
Journal of the American Chemical Society, Jun 1, 1984
In this paper we report the results of our calculations on the title compounds using the LCAO-MO ... more In this paper we report the results of our calculations on the title compounds using the LCAO-MO Hartree-Fock-Slater method, including relativistic effects. Excellent agreement is obtained between the computed and experimentally reported ionization potentials for each of the molecules. The results point toward a new assignment of the ultraviolet photoelectron spectra in the region of the dl0 ionization bands. In particular, an ionization event from an orbital that contains a large component of d, is stabilized in all of the compounds except Hg(CH3)2, relative to the spin-orbit components composed mainly of the d, and d6 orbitals. The net contribution of the metal d electrons to the overall bonding is only about 10% for the Hg compounds but approaches 40% for the Au-PH3 bond of the model compound Au(PH3)(CH3). Calculations also have been carried out without the use of 6p orbitals to show that these orbitals contribute only slightly to the bond strength. The picture that emerges is that at least 80% of the bonding for the Hg compounds is due to the 6s orbital on the Hg atom, and hence the bonding is best described in terms of a three-center two-electron bond. This description is shown to be in agreement with the known relative bond strengths of group 2 metal halides MX2, wherein removal of the first X atom to form MX requires much more
![Research paper thumbnail of A Density Functional Study of the MLCT States of [Ru(bpy)3]2+ in D3 Symmetry](https://attachments.academia-assets.com/111077737/thumbnails/1.jpg)
](Inorganic Chemistry, Aug 1, 1994
A density functional based first principles study of the metal to ligand charge-transfer (MLCT) s... more A density functional based first principles study of the metal to ligand charge-transfer (MLCT) states of [Ru-(bpy)312+ is presented. The method used in this study includes first-order electrostatic multiplet splitting as well as spin-orbit interaction. The results obtained show that there is an important mixing of the excited singlet and triplet states. These first principles results are in good overall agreement with the observed absorption spectra, with respect to both the spread of the excitation energies and the positions of the strong, unambiguously assigned peaks. Our calculation finds the lowest excited states to be virtually degenerate A1 and E spin-orbit components of the (dr:al)-(r*:az) 3A2 state, the former lying a few 10-cm-1 units below the latter one. The next excited triplet, i.e. (dr:e)-(r*:az) 3E, arises only roughly 1500 cm-I above the 3A2.
Physical Chemistry Chemical Physics, 2016
Probabilities of single ionization channels or double and multiple simultaneous ionization can be... more Probabilities of single ionization channels or double and multiple simultaneous ionization can be determined from exact master equations for time-dependent Dyson orbitals.
Journal of the American Chemical Society, 1996
The definition of the virtual torsion angle as shown in Figure 2 (CR1, CR2, CR3 N4) does not matc... more The definition of the virtual torsion angle as shown in Figure 2 (CR1, CR2, CR3 N4) does not match that of Ball et al. (refs 14 and 74: carbonyl carbon 1, CR2, CR3, N4). Using the corrected definition of has little effect on Figure 5 and does not alter the conclusions of the paper. Figure 5B calculated using the corrected definition of is given in the supporting information. Figure 5B calculated using the corrected definition of (1 page). This material is contained in many libraries on microfiche, immediately follows this article in the microfilm version of the journal, can be ordered from the ACS, and can be downloaded from the Internet; see any current masthead page for ordering information and Internet access instructions.
In this paper, the history, present status, and future of density-functional theory (DFT) is info... more 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 exchange views on DFT in the form of 300 individual contributions, formulated as responses to a preset list of 26 questions. Supported by a bibliography of 776 entries, the paper represents a broad snapshot of DFT, anno 2022.
International Journal of Quantum Chemistry, 2006
The discovery by Kool and coworkers that 2,4‐difluorotoluene (F) mimics thymine (T) in DNA replic... more The discovery by Kool and coworkers that 2,4‐difluorotoluene (F) mimics thymine (T) in DNA replication has led to controversy regarding the question of whether this mimic has the capability of forming hydrogen bonds with adenine (A). Recently, we have provided evidence for an important role of both hydrogen bonding and steric effects in the replication of DNA. In the present work, we extend our study to mimics (GFC′N′ and CN′NF) of the bases guanine (G) and cytosine (C). We address not only the question of the strengths of the hydrogen bonds in GFC′N′CN′NF as compared with those in GC but we focus in particular on the nature of these interactions. Thus, we have analyzed GFC′N′CN′NF and GC at the BP86/TZ2P level of density functional theory (DFT). In line with previous experience, this approach is shown to achieve close agreement with the available data from ab initio computations and experiment: the complexation energy of GFC′N′CN′NF (‐4.1 kcal/mol) is confirmed to be much weaker indeed than that of GC (‐26.1 kcal/mol). Interestingly, the weak hydrogen bonds in GFC′N′CN′NF still poses a significant orbital interaction component that resembles the situation for the more strongly bound GC, as follows from (1) an analysis of the orbital electronic structure of GFC′N′CN′NF and GC, (2) a quantitative decomposition of the GFC′N′CN′NF and GC bond energies, as well as (3) a quantitative decomposition of the charge redistribution associated with the GFC′N′ CN′NF and GC interactions based on the Voronoi deformation density (VDD) method. The VDD method allows us to decompose the charge redistribution ΔQ per atom into a component associated with the Pauli repulsive orbital interactions and a component associated with the bonding orbital interactions: ΔQ = ΔQPauli + ΔQoi. Implications of our findings for the mechanism of DNA replication are discussed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Journal of Chemical Physics, Sep 1, 1992
The influence of relativity on the binding in the Pt–O molecule is investigated using density fun... more The influence of relativity on the binding in the Pt–O molecule is investigated using density functional calculations and proves to be quite important, not only for the potential well but also for the repulsive wall. Using a Born–Mayer fit to this interatomic gas phase potential, we perform a classical trajectory study on high energy O2/Pt(111) scattering (Ei=80 eV). The Born–Mayer form of the interatomic potential leads to a higher degree of dissociation for O2/Pt(111) than for O2/Ag(111) which is also experimentally found. The role of relativity turns out to be significant. The dissociation mechanism, however, does not change when going from O2/Ag(111) to O2/Pt(111). The molecules were found to first gain primarily rotational energy, which is largely transfered to vibration at the turning point of the second atom, in the case of finally dissociating molecules. Since the calculated dissociation in the case of platinum is still less than found experimentally, we investigate the influence of better fits to the interatomic potential, as well as inclusion of the potential well. It is possible to improve agreement with the experimental results by directly reducing the long range of the Born–Mayer potential.
ChemInform, 2010
ABSTRACT The strength of the CN/CN′ bond decreases in the series NC-CN (1), CN-CN (2), and CN-NC ... more ABSTRACT 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 repulsion between the 4σ and 5σ orbitals; (c) donor/acceptor interaction between the 4σ and 5σ orbitals; (d) donor/acceptor interaction between the occupied 1π and unoccupied 2π*. Each of these contributions is numerically significant. The singly occupied 5σ plays, apart from the pair bonding, a dual role, causing Pauli repulsion (with the N lone pair) as an occupied orbital and causing charge-transfer interaction in its capacity of unoccupied acceptor orbital. Detailed consideration of the balance between the repulsive and attractive energy components and their R dependence is required to explain why the central CN/CN′ bond considerably weakens when going from 1 to 3, and why it still contracts. Density functionals that include gradient corrections for the exchange and electron gas parametrization for correlation between electrons of different spin (but no same-spin correlation) are shown to achieve an accuracy for the systems under consideration which is comparable to that of conventional high-level ab initio methods like CEPA and the CCD(+ST) coupled cluster approach.
Perfils Evert Jan Baerends i la densitat electrònica de molècules Com és que la química computaci... more Perfils Evert Jan Baerends i la densitat electrònica de molècules Com és que la química computacional, una disciplina que requereix ordinadors potentíssims per avançar, alhora també es pot expressar amb un llapis i un paper? Per dir-ho senzill, treballem amb equacions que es poden resoldre molt fàcilment en un paper, però els sistemes als quals les apliquem són tan complexos que requereixen la potència de càlcul que donen els grans computadors, que necessiten dies o setmanes per proporcionar resultats. Per què la química computacional no forma part del bagatge de tots els químics i, en canvi, s'ha constituït com un camp amb personalitat pròpia? El desenvolupament de la teoria i, més endavant, de programes informàtics, ha estat molt complex i difícil. Aquest és el motiu
Journal of Chemical Physics, Nov 15, 2000
and it is a condition of accessing publications that users recognise and abide by the legal requi... more and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Journal of Chemical Physics, May 15, 2000
and it is a condition of accessing publications that users recognise and abide by the legal requi... more and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Journal of Chemical Theory and Computation, Jul 27, 2022
Physical Chemistry Chemical Physics, 2022
Chemical Physics Letters, Dec 1, 2006
It is well known, that second-order perturbation theory (PT2) breaks down when the gap between th... more It is well known, that second-order perturbation theory (PT2) breaks down when the gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied MO (LUMO) becomes too low. It is demonstrated that when the local Kohn–Sham (KS) potential vs is approximated by an expansion in a set of basis functions, exact HOMO–LUMO degeneracy occurs, if a finite orbital
Journal of Chemical Physics, Oct 23, 2008
A recently proposed series of corrections to the earliest JK-only functionals has considerably im... more A recently proposed series of corrections to the earliest JK-only functionals has considerably improved the prospects of density matrix functional theory ͑DMFT͒. Still, the most advanced of these functionals ͑correction C3͒ requires a preselection of the terms in the pair density ⌫͑r 1 , r 2 ͒ involving the bonding and antibonding natural orbitals ͑NOs͒ belonging to an electron pair bond. Ideally, a DMFT functional should only depend on the NOs and their occupation numbers, and we propose a functional with an occupation number driven weighing of terms in the pair density. These are formulated as "damping" for certain ranges of occupation numbers of the two-electron cumulant that arises in the expansion of the two-particle density matrix of the paradigmatic two-electron system. This automatic version of C3, which we denote AC3, provides the correct dissociation limit for electron pair bonds and it excellently reproduces the potential energy curves of the multireference configuration interaction ͑MRCI͒ method for the dissociation of the electron pair bond in the series of the ten-electron hydrides CH 4 , NH 3 , H 2 O, and HF. AC3 reproduces closely the experimental equilibrium distances and at R e it yields correlation energies of the ten-electron systems with an average error in the absolute values of only 3.3% compared to the MRCI values. We stress the importance of treatment of strong correlation cases ͑NO occupation numbers differing significantly from 2.0 and 0.0͒ by appropriate terms in the cumulant.
Surface Science, May 1, 1994
ABSTRACT
Physical review, Oct 15, 1986
Journal of Molecular Structure-theochem, Apr 1, 2006
For functionals that depend on the Kohn-Sham orbitals, the optimized effective potential method (... more For functionals that depend on the Kohn-Sham orbitals, the optimized effective potential method (OEP) of density functional theory (DFT) seeks a lowest energy solution by finding that particular local potential v s for which a stationary value of the energy is obtained, dE/dv s Z0. We assess the performance of a particular method of solution, namely the expansion of v s , or the rest term v s-v 0 , in a finite set of expansion functions, using the exact exchange functional (EXX) as the simplest realistic orbital dependent functional. Here, v 0 is a fixed local potential having the longrange asymptotics K1/r. For some prototype small systems the interdependence of the basis sets for the Kohn-Sham orbitals and for the potential has been investigated, as well as the effect of the reference potential v 0. We specifically address the numerical precision with which the total energy E EXX and the orbital energies f3 EXX i g can be obtained. The EXX solution is obtained both with and without explicitly imposing the 'HOMO condition' that the energy 3 H of the highest occupied molecular orbital be equal to the expectation value of the Fock operator. The potential expansion method yields reliable total energies even without the use of a reference potential (v 0 Z0). However, the reliability of the calculated orbital energies remains a serious problem. Without the HOMO condition even the use of reference potentials with correct asymptotics cannot prevent an uncontrolled shift of the orbital energies. Imposing the HOMO condition solves this problem. But even with this condition imposed, the accuracy of other orbital energies is, typically, many orders of magnitude lower than that for the total energy.
Journal of Physical Chemistry A, Jul 1, 2003
The formation of active intermediates from the Fenton-like reagent (a mixture of iron(III) ions a... more The formation of active intermediates from the Fenton-like reagent (a mixture of iron(III) ions and hydrogen peroxide) in aqueous solution has been investigated using static DFT calculations and Car-Parrinello molecular dynamics simulations. We show the spontaneous formation of the iron(III) hydroperoxo intermediate in a first step. The Fenton-like reaction thus proceeds very differently compared to Fenton's reagent (i.e., the Fe II /H 2 O 2 mixture), for which we have recently shown that the first step is the spontaneous O-O lysis of hydrogen peroxide when coordinated to iron(II) in water. For the second step in the reaction mechanism of the Fenton-like reagent, we compare the possibilities of homolysis and heterolysis of the O-O bond and the Fe-O bond of the produced [(H 2 O) 5 Fe III OOH] 2+ intermediate. We find that concomitant hydrolysis of the reacting species plays a crucial role and, taking this into account, that O-O homolysis ([(H 2 O) 4 (OH)Fe III-OOH] + f [(H 2 O) 4 (OH)Fe IV O] + + OH •) in vacuo is a likely second step with ∆E 0k ‡) 26 kcal/mol. However, proper inclusion of the solvent effects is important, in particular, for the heterolysis reactions, in which case the large endothermicy of the charge separations can be compensated by the hydration energies from the ion solvation. In this work, we also calculate the free energy barrier for the O-O homolysis of the iron(III) hydroperoxo intermediate in aqueous solution at T) 300 K, using the method of constrained molecular dynamics and thermodynamic integration, resulting in ∆A 300K ‡) 21 kcal/mol. Analysis of the vibrational spectra of the high-spin (S) 5/2) and low-spin (S) 1/2) Fe(III)OOH intermediates confirm the, in the literature, suggested effect of the spin state on the Fe-O and O-O bond strengths. In fact, we predict that with ligands inducing a low-spin iron(III) hydroperoxo intermediate, the barrier for the O-O homolysis will be even significantly lower.
Journal of the American Chemical Society, Jun 1, 1984
In this paper we report the results of our calculations on the title compounds using the LCAO-MO ... more In this paper we report the results of our calculations on the title compounds using the LCAO-MO Hartree-Fock-Slater method, including relativistic effects. Excellent agreement is obtained between the computed and experimentally reported ionization potentials for each of the molecules. The results point toward a new assignment of the ultraviolet photoelectron spectra in the region of the dl0 ionization bands. In particular, an ionization event from an orbital that contains a large component of d, is stabilized in all of the compounds except Hg(CH3)2, relative to the spin-orbit components composed mainly of the d, and d6 orbitals. The net contribution of the metal d electrons to the overall bonding is only about 10% for the Hg compounds but approaches 40% for the Au-PH3 bond of the model compound Au(PH3)(CH3). Calculations also have been carried out without the use of 6p orbitals to show that these orbitals contribute only slightly to the bond strength. The picture that emerges is that at least 80% of the bonding for the Hg compounds is due to the 6s orbital on the Hg atom, and hence the bonding is best described in terms of a three-center two-electron bond. This description is shown to be in agreement with the known relative bond strengths of group 2 metal halides MX2, wherein removal of the first X atom to form MX requires much more
Inorganic Chemistry, Aug 1, 1994
A density functional based first principles study of the metal to ligand charge-transfer (MLCT) s... more A density functional based first principles study of the metal to ligand charge-transfer (MLCT) states of [Ru-(bpy)312+ is presented. The method used in this study includes first-order electrostatic multiplet splitting as well as spin-orbit interaction. The results obtained show that there is an important mixing of the excited singlet and triplet states. These first principles results are in good overall agreement with the observed absorption spectra, with respect to both the spread of the excitation energies and the positions of the strong, unambiguously assigned peaks. Our calculation finds the lowest excited states to be virtually degenerate A1 and E spin-orbit components of the (dr:al)-(r*:az) 3A2 state, the former lying a few 10-cm-1 units below the latter one. The next excited triplet, i.e. (dr:e)-(r*:az) 3E, arises only roughly 1500 cm-I above the 3A2.
Physical Chemistry Chemical Physics, 2016
Probabilities of single ionization channels or double and multiple simultaneous ionization can be... more Probabilities of single ionization channels or double and multiple simultaneous ionization can be determined from exact master equations for time-dependent Dyson orbitals.
Journal of the American Chemical Society, 1996
The definition of the virtual torsion angle as shown in Figure 2 (CR1, CR2, CR3 N4) does not matc... more The definition of the virtual torsion angle as shown in Figure 2 (CR1, CR2, CR3 N4) does not match that of Ball et al. (refs 14 and 74: carbonyl carbon 1, CR2, CR3, N4). Using the corrected definition of has little effect on Figure 5 and does not alter the conclusions of the paper. Figure 5B calculated using the corrected definition of is given in the supporting information. Figure 5B calculated using the corrected definition of (1 page). This material is contained in many libraries on microfiche, immediately follows this article in the microfilm version of the journal, can be ordered from the ACS, and can be downloaded from the Internet; see any current masthead page for ordering information and Internet access instructions.
In this paper, the history, present status, and future of density-functional theory (DFT) is info... more 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 exchange views on DFT in the form of 300 individual contributions, formulated as responses to a preset list of 26 questions. Supported by a bibliography of 776 entries, the paper represents a broad snapshot of DFT, anno 2022.
International Journal of Quantum Chemistry, 2006
The discovery by Kool and coworkers that 2,4‐difluorotoluene (F) mimics thymine (T) in DNA replic... more The discovery by Kool and coworkers that 2,4‐difluorotoluene (F) mimics thymine (T) in DNA replication has led to controversy regarding the question of whether this mimic has the capability of forming hydrogen bonds with adenine (A). Recently, we have provided evidence for an important role of both hydrogen bonding and steric effects in the replication of DNA. In the present work, we extend our study to mimics (GFC′N′ and CN′NF) of the bases guanine (G) and cytosine (C). We address not only the question of the strengths of the hydrogen bonds in GFC′N′CN′NF as compared with those in GC but we focus in particular on the nature of these interactions. Thus, we have analyzed GFC′N′CN′NF and GC at the BP86/TZ2P level of density functional theory (DFT). In line with previous experience, this approach is shown to achieve close agreement with the available data from ab initio computations and experiment: the complexation energy of GFC′N′CN′NF (‐4.1 kcal/mol) is confirmed to be much weaker indeed than that of GC (‐26.1 kcal/mol). Interestingly, the weak hydrogen bonds in GFC′N′CN′NF still poses a significant orbital interaction component that resembles the situation for the more strongly bound GC, as follows from (1) an analysis of the orbital electronic structure of GFC′N′CN′NF and GC, (2) a quantitative decomposition of the GFC′N′CN′NF and GC bond energies, as well as (3) a quantitative decomposition of the charge redistribution associated with the GFC′N′ CN′NF and GC interactions based on the Voronoi deformation density (VDD) method. The VDD method allows us to decompose the charge redistribution ΔQ per atom into a component associated with the Pauli repulsive orbital interactions and a component associated with the bonding orbital interactions: ΔQ = ΔQPauli + ΔQoi. Implications of our findings for the mechanism of DNA replication are discussed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Journal of Chemical Physics, Sep 1, 1992
The influence of relativity on the binding in the Pt–O molecule is investigated using density fun... more The influence of relativity on the binding in the Pt–O molecule is investigated using density functional calculations and proves to be quite important, not only for the potential well but also for the repulsive wall. Using a Born–Mayer fit to this interatomic gas phase potential, we perform a classical trajectory study on high energy O2/Pt(111) scattering (Ei=80 eV). The Born–Mayer form of the interatomic potential leads to a higher degree of dissociation for O2/Pt(111) than for O2/Ag(111) which is also experimentally found. The role of relativity turns out to be significant. The dissociation mechanism, however, does not change when going from O2/Ag(111) to O2/Pt(111). The molecules were found to first gain primarily rotational energy, which is largely transfered to vibration at the turning point of the second atom, in the case of finally dissociating molecules. Since the calculated dissociation in the case of platinum is still less than found experimentally, we investigate the influence of better fits to the interatomic potential, as well as inclusion of the potential well. It is possible to improve agreement with the experimental results by directly reducing the long range of the Born–Mayer potential.
ChemInform, 2010
ABSTRACT The strength of the CN/CN′ bond decreases in the series NC-CN (1), CN-CN (2), and CN-NC ... more ABSTRACT 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 repulsion between the 4σ and 5σ orbitals; (c) donor/acceptor interaction between the 4σ and 5σ orbitals; (d) donor/acceptor interaction between the occupied 1π and unoccupied 2π*. Each of these contributions is numerically significant. The singly occupied 5σ plays, apart from the pair bonding, a dual role, causing Pauli repulsion (with the N lone pair) as an occupied orbital and causing charge-transfer interaction in its capacity of unoccupied acceptor orbital. Detailed consideration of the balance between the repulsive and attractive energy components and their R dependence is required to explain why the central CN/CN′ bond considerably weakens when going from 1 to 3, and why it still contracts. Density functionals that include gradient corrections for the exchange and electron gas parametrization for correlation between electrons of different spin (but no same-spin correlation) are shown to achieve an accuracy for the systems under consideration which is comparable to that of conventional high-level ab initio methods like CEPA and the CCD(+ST) coupled cluster approach.
Perfils Evert Jan Baerends i la densitat electrònica de molècules Com és que la química computaci... more Perfils Evert Jan Baerends i la densitat electrònica de molècules Com és que la química computacional, una disciplina que requereix ordinadors potentíssims per avançar, alhora també es pot expressar amb un llapis i un paper? Per dir-ho senzill, treballem amb equacions que es poden resoldre molt fàcilment en un paper, però els sistemes als quals les apliquem són tan complexos que requereixen la potència de càlcul que donen els grans computadors, que necessiten dies o setmanes per proporcionar resultats. Per què la química computacional no forma part del bagatge de tots els químics i, en canvi, s'ha constituït com un camp amb personalitat pròpia? El desenvolupament de la teoria i, més endavant, de programes informàtics, ha estat molt complex i difícil. Aquest és el motiu