Showing papers in "International Journal of Quantum Chemistry in 2016"
TL;DR: In this article, the authors present a tutorial for the simulation of vibrational and vibrationally resolved electronic spectra of medium-to-large molecules, including thiophene and its smallest oligomer bithiophene.
Abstract: In this tutorial review, we present some effective methodologies available for the simulation of vibrational and vibrationally resolved electronic spectra of medium-to-large molecules. They have been integrated into a unified platform and extended to support a wide range of spectroscopies. The resulting tool is particularly useful in assisting the extensive characterization of molecules, often achieved by combining multiple types of measurements. A correct assessment of the reliability of theoretical calculations is a necessary prelude to the interpretation of their results. For this reason, the key concepts of the underlying theories will be first presented and then illustrated through the study of thiophene and its smallest oligomer, bithiophene. While doing so, a complete computational protocol will be detailed, with emphasis on the strengths and potential shortcomings of the models employed here. Guidelines are also provided for performing similar studies on different molecular systems, with comments on the more common pitfalls and ways to overcome them. Finally, extensions to other cases, like chiral spectroscopies or mixtures, are also discussed.
157 citations
TL;DR: In this paper, Kernel ridge regression is used to approximate the kinetic energy of non-interacting fermions in a one dimensional box as a functional of their density, and a projected gradient descent algorithm is derived using local principal component analysis.
Abstract: Machine learning (ML) is an increasingly popular statistical tool for analyzing either measured or calculated data sets. Here, we explore its application to a well-defined physics problem, investigating issues of how the underlying physics is handled by ML, and how self-consistent solutions can be found by limiting the domain in which ML is applied. The particular problem is how to find accurate approximate density functionals for the kinetic energy (KE) of noninteracting electrons. Kernel ridge regression is used to approximate the KE of non-interacting fermions in a one dimensional box as a functional of their density. The properties of different kernels and methods of cross-validation are explored, reproducing the physics faithfully in some cases, but not others. We also address how self-consistency can be achieved with information on only a limited electronic density domain. Accurate constrained optimal densities are found via a modified Euler-Lagrange constrained minimization of the machine-learned total energy, despite the poor quality of its functional derivative. A projected gradient descent algorithm is derived using local principal component analysis. Additionally, a sparse grid representation of the density can be used without degrading the performance of the methods. The implications for machine-learned density functional approximations are discussed. © 2015 Wiley Periodicals, Inc.
143 citations
TL;DR: Real-time time-dependent functional theory (RT-TDDFT) as discussed by the authors directly propagates the electron density in the time domain by integrating the timedependent Kohn-Sham equations, in contrast to the popular linear response TDDFT matrix formulation that computes transition frequencies from a ground state reference.
Abstract: Real-time time-dependent functional theory (RT-TDDFT) directly propagates the electron density in the time domain by integrating the time-dependent Kohn–Sham equations. This is in contrast to the popular linear response TDDFT matrix formulation that computes transition frequencies from a ground state reference. RT-TDDFT is, therefore, a potentially powerful technique for modeling atto- to picosecond electron dynamics, including charge transfer pathways, the response to a specific applied field, and frequency dependent linear and nonlinear properties. However, qualitatively incorrect electron dynamics and time-dependent resonant frequencies can occur when perturbing the density away from the ground state due to the common adiabatic approximation. An overview of the RT-TDDFT method is provided here, including examples of some cases that lead to this qualitatively incorrect behavior. © 2016 Wiley Periodicals, Inc.
117 citations
TL;DR: In this article, the effects of using thermal and quantum samplings are analyzed taking pyrrole as a test case, and it is shown that there are significant differences in the results obtained with each two approaches.
Abstract: Semiclassical simulations of spectrum and dynamics of complex molecules require statistical sampling of coordinates and momenta. The effects of using thermal and quantum samplings are analyzed taking pyrrole as a test case. It is shown that there are significant differences in the results obtained with each of these two approaches. Overall, quantum sampling based on a Wigner distribution renders superior results, comparing well to the experiments. Dynamics simulations based on surface hopping and ADC(2) reveal that pyrrole internal conversion to the ground state occurs not only through H-elimination path, but also through ring-distortion paths, which have been systematically neglected by diverse experimental setups. The analysis of the reaction paths also shows that the ionization potential varies by more than 5 eV between ionization of the excited state at the Franck-Condon region and at the intersections with the ground state. This feature may have major implications for time-resolved photoelectron spectroscopy. (c) 2015 Wiley Periodicals, Inc.
117 citations
TL;DR: In this paper, the authors present the theory of semilocal exchange-correlation (XC) energy functionals which depend on the Kohn-Sham kinetic energy density (KED), including meta-generalized gradient approximation (meta-GGA) functionals.
Abstract: We present the theory of semilocal exchange-correlation (XC) energy functionals which depend on the Kohn–Sham kinetic energy density (KED), including the relevant class of meta-generalized gradient approximation (meta-GGA) functionals. Thanks to the KED ingredient, meta-GGA functionals can satisfy different exact constraints for XC energy and can be made one-electron self-correlation free. This leads to a better accuracy over a wider range of properties with respect to GGAs, often reaching the accuracy of hybrid functionals, but at much reduced computational cost. An extensive survey of the relevant literature on existing KED dependent XC functionals is provided, considering nonempirical, semi-empirical, and fully empirical ones. A deeper analysis and a wide benchmark are presented for functionals derived considering only exact constraints and parameters obtained from model and/or atomic systems.
101 citations
TL;DR: The best ReaxFF potential was trained from 848 data points and could reliably predict surface and bulk data and was substantially less accurate for molecular clusters of 126 atoms or fewer; however, the BPNN potential in this implementation brings significantly higher computational cost.
Abstract: We have studied how ReaxFF and Behler–Parrinello neural network (BPNN) atomistic potentials should be trained to be accurate and tractable across multiple structural regimes of Au as a representative example of a single-component material. We trained these potentials using subsets of 9,972 Kohn-Sham density functional theory calculations and then validated their predictions against the untrained data. Our best ReaxFF potential was trained from 848 data points and could reliably predict surface and bulk data; however, it was substantially less accurate for molecular clusters of 126 atoms or fewer. Training the ReaxFF potential to more data also resulted in overfitting and lower accuracy. In contrast, BPNN could be fit to 9,734 calculations, and this potential performed comparably or better than ReaxFF across all regimes. However, the BPNN potential in this implementation brings significantly higher computational cost. © 2016 Wiley Periodicals, Inc.
78 citations
TL;DR: In this paper, a recently developed integrated Quantum-Mechanical/Polarizable molecular mechanics (MM)/polarizable continuum model (PCM) method is discussed, which combines a fluctuating charge approach to the MM polarization with the PCM.
Abstract: Solvent effects on chiroptical properties and spectroscopies can be huge, and affect not only the absolute value but the sign of molecular chiroptical responses. Therefore, the definition of reliable theoretical models and computational protocols to calculate chiroptical responses and assist the assignment of the chiral absolute configuration cannot overlook the effects of the surrounding environment. Continuum solvation methodologies are successful in case of weakly interacting solute–solvent couples, whereas in case of strongly interacting systems, such as those dominated by explicit hydrogen bonding interaction, a change of strategy is required to gain a reliable modeling. In this review, a recently developed integrated Quantum-Mechanical/Polarizable molecular mechanics (MM)/polarizable continuum model (PCM) method is discussed, which combines a fluctuating charge approach to the MM polarization with the PCM. Its theoretical fundamentals, and issues related to the calculation of chiroptical responses are summarized, and the application to few representative test cases in aqueous solution is discussed.
76 citations
TL;DR: The statistical nature of nonadiabatic transition state theory (NA-TST) provides an elegant and computationally inexpensive way to calculate the rate constants for intersystem crossings, spin-forbidden reactions, and spin-crossovers in large complex systems as discussed by the authors.
Abstract: Nonadiabatic transition state theory (NA-TST) is a powerful tool to investigate the nonradiative transitions between electronic states with different spin multiplicities. The statistical nature of NA-TST provides an elegant and computationally inexpensive way to calculate the rate constants for intersystem crossings, spin-forbidden reactions, and spin-crossovers in large complex systems. The relations between the microcanonical and canonical versions of NA-TST and the traditional transition state theory are shown, followed by a review of the basic steps in a typical NA-TST rate constant calculation. These steps include evaluations of the transition probability and coupling between electronic states with different spin multiplicities, a search for the minimum energy crossing point (MECP), and computing the densities of states and partition functions for the reactant and MECP structures. The shortcomings of the spin-diabatic version of NA-TST related to ill-defined state coupling and state counting are highlighted. In three examples, we demonstrate the application of NA-TST to intersystem crossings in the active sites of metal-sulfur proteins focusing on [NiFe]-hydrogenase, rubredoxin, and Fe2S2-ferredoxin. © 2016 Wiley Periodicals, Inc.
64 citations
TL;DR: Usefulness and advantages that can be gained by exploiting VR are reported, considering few examples specifically selected to illustrate different level of theory and molecular representation.
Abstract: The role of Virtual Reality (VR) tools in molecular sciences is analyzed in this contribution through the presentation of the Caffeine software to the quantum chemistry community. Caffeine, developed at Scuola Normale Superiore, is specifically tailored for molecular representation and data visualization with VR systems, such as VR theaters and helmets. Usefulness and advantages that can be gained by exploiting VR are here reported, considering few examples specifically selected to illustrate different level of theory and molecular representation.
54 citations
TL;DR: In this paper, generalized relativistic effective core potentials (GRECPs) have been generated for actinides to perform accurate calculations of electronic structure and properties of their compounds with moderate computational cost.
Abstract: Actinide compounds are very intriguing objects for the quantum chemistry because, on the one hand, these compounds are of great scientific and technological interest and, on the other hand, quantitative first principle based modeling of their electronic structure is extremely difficult because of strong relativistic effects and complicated electron correlation pattern. The efficiency of high-level all-electron relativistic methods in applications to complex actinide systems of practical interest is questionable and more economical but sufficiently accurate approaches to the studies of such systems are preferable. Recently, generalized relativistic effective core potentials (GRECPs) have been generated for actinides to perform accurate calculations of electronic structure and properties of their compounds with moderate computational cost. The accuracy of different GRECP versions is analyzed in atomic calculations and their applications to molecular and cluster calculations are reviewed. The results are compared with available experimental data and other theoretical studies. © 2015 Wiley Periodicals, Inc.
51 citations
TL;DR: In this article, critical parameters in three screened potentials, namely, Hulthen, Yukawa and exponential cosine screened Coulomb potential, for all states having $n \leq 10$ were reported.
Abstract: Critical parameters in three screened potentials, namely, Hulthen, Yukawa and exponential cosine screened Coulomb potential are reported. Accurate estimates of these parameters are given for each of these potentials, for all states having $n \leq 10$. Comparison with literature results is made, wherever possible. Present values compare excellently with reference values; for higher $n,\ell$, our results are slightly better. Some of these are presented for first time. Further, we investigate the spherical confinement of H atom embedded in a dense plasma modeled by an exponential cosine screened potential. Accurate energies along with their variation with respect to box size and screening parameter are calculated and compared with reference results in literature. Sample dipole polarizabilities are also provided in this case. The generalized pseudospectral method is used for accurate determination of eigenvalues and eigenfunctions for all calculations.
TL;DR: In this paper, the authors provide an overview of the computational strategies that permit accurate equilibrium structure determinations for systems ranging from small molecules to medium-sized building-blocks of biomolecules.
Abstract: Molecular structure is one of the most relevant concepts in chemistry. It plays a central role in determining molecular and spectroscopic properties: a mandatory prerequisite for a thorough understanding of the chemical and physical properties of molecules is in fact represented by the knowledge of their geometrical structures. While in some fields a qualitative description of the molecular structure might be sufficient, in many others, like for example spectroscopy, a quantitative, and accurate determination is mandatory. Nowadays, the most advanced computational methodologies allow reliable structural predictions able to fulfil the proper accuracy requirements. This contribution provides an overview on this topic, focusing on the computational strategies that permit accurate equilibrium structure determinations for systems ranging from small molecules to medium-sized building-blocks of biomolecules.
TL;DR: In this paper, an efficient quantum algorithm for beyond-Born-Oppenheimer molecular energy computations is presented, which combines the quantum full configuration interaction method with the nuclear orbital plus molecular orbital method.
Abstract: We present an efficient quantum algorithm for beyond-Born–Oppenheimer molecular energy computations. Our approach combines the quantum full configuration interaction method with the nuclear orbital plus molecular orbital method. We give the details of the algorithm and demonstrate its performance by classical simulations. Two isotopomers of the hydrogen molecule (H2, HT) were chosen as representative examples and calculations of the lowest rotationless vibrational transition energies were simulated. © 2016 Wiley Periodicals, Inc.
TL;DR: This work discusses six questions related to the recent “strongly constrained and appropriately normed” (SCAN) meta-generalized gradient approximation (meta-GGA) and investigates whether semilocal functionals make consistent predictions for the energy differences between different molecules.
Abstract: We discuss six questions related to the recent “strongly constrained and appropriately normed” (SCAN) meta-generalized gradient approximation (meta-GGA): (1) When and why should a semilocal approximation to the density functional for the exchange-correlation energy be accurate? (2) What is the right dimensionless ingredient for a meta-GGA, and why? (3) In the construction of density functional approximations, should we satisfy more or fewer exact constraints? (4) Is there a tight lower bound on the exchange energy for all spin-unpolarized densities? (5) Should a semilocal approx- imation yield any intermediate-range van der Waals interaction? (6) Do semilocal functionals make consistent predictions for the energy differences between different molecules (and thus presumably for reaction and formation energies)? © 2016 Wiley Periodicals, Inc.
TL;DR: In this article, the substituent effects in aerogen bond interactions between ZO3 and different nitrogen bases are studied at the MP2/aug-cc-pVTZ level of theory.
Abstract: The substituent effects in aerogen bond interactions between ZO3 (Z = Kr, Xe) and different nitrogen bases are studied at the MP2/aug-cc-pVTZ level of theory. The nitrogen bases include the sp bases NCH, NCF, NCCl, NCBr, NCCN, NCOH, NCCH3 and the sp3 bases NH3, NH2F, NH2Cl, NH2Br, NH2CN, NH2OH, and NH2CH3. The nature of aerogen bonds in these complexes is analyzed by means of molecular electrostatic potential, electron localization function, quantum theory atoms in molecules, noncovalent interaction index, and natural bond orbital analyses. The interaction energy (Eint) ranges from −4.59 to −9.65 kcal/mol in the O3Z···NCX complexes and from −5.30 to −13.57 kcal/mol in the O3Z···NH2X ones. The dominant charge-transfer interaction in these complexes occurs across the aerogen bond from the nitrogen lone-pair (nN) of the Lewis base to the σ*Z-O antibonding orbital of the ZO3. Besides, the formation of aerogen bond tends to decrease the 83Kr or 131Xe chemical shielding values in these complexes. © 2016 Wiley Periodicals, Inc.
TL;DR: In this article, rational design strategies for pure organic high-spin molecules with strong intramolecular magnetic interactions are presented, mostly focusing on the design of ferromagnetically coupled organic diradicals.
Abstract: In this review, rational design strategies for pure organic high-spin molecules with strong intramolecular magnetic interactions are presented, mostly focusing on the design of ferromagnetically coupled organic diradicals. After brief introduction of the calculation procedure for intramolecular magnetic coupling constant J using density functional theory (DFT), classification and standardization of magnetic character of well-known stable radicals and coupler units are discussed. Following the development of general strategy for the design of organic high-spin diradical by means of the classification and standardization scheme, applicability of the strategy for making pendent-type organic polyradical using zigzag graphene nanoribbons backbone is demonstrated. In a computational point of view, a scaling procedure and an optimization of Hartree–Fock exact exchange ratio of a hybrid DFT functional for better prediction of the J of diradicals are discussed. © 2015 Wiley Periodicals, Inc.
TL;DR: In this article, the structural, electronic, and magnetic properties of 3D transition-metal atoms doped 2D GaN nanosheet were investigated and the results showed that substituting a 3D TM atom with one Ga leads to a structural reconstruction around the 3d TM impurity.
Abstract: We have performed the first-principles calculations on the structural, electronic, and magnetic properties of 3d transition-metal™ (Cr, Mn, Fe, Co, and Ni) atoms doped 2D GaN nanosheet. The results show that 3d TM atom substituting one Ga leads to a structural reconstruction around the 3d TM impurity compared to the pristine GaN nanosheet. The doping of TM atom can induce magnetic moments, which are mainly located on the 3d TM atom and its nearest-neighbor N atoms. It is found that Mn- and Ni-doped GaN nanosheet with 100% spin polarization characters seem to be good candidates for spintronic applications. When two Ga atoms are substituted by two TM dopants, the ferromagnetic (FM) ordering becomes energetically more favorable for Cr-, Mn-, and Ni-doped GaN nanosheet with different distances of two TM atoms. On the contrary, the antiferromagnetic (AFM) ordering is energetically more favorable for Fe-doped GaN nanosheet. In addition, our GGA + U calculations show the similar results with GGA calculations. © 2016 Wiley Periodicals, Inc.
TL;DR: In this paper, the state-of-the-art in the area of quantum-chemical modeling of electron transfer (ET) processes at metal electrode/electrolyte solution interfaces is reviewed.
Abstract: State-of-the-art in the area of quantum-chemical modeling of electron transfer (ET) processes at metal electrode/electrolyte solution interfaces is reviewed. Emphasis is put on key quantities which control the ET rate (activation energy, transmission coefficient, and work terms). Orbital overlap effect in electrocatalysis is thoroughly discussed. The advantages and drawbacks of cluster and periodical slab models for a metal electrode when describing redox processes are analyzed as well. It is stressed that reliable quantitative estimations of the rate constants of interfacial charge transfer reactions are hardly possible, while predictions of qualitatively interesting effects are more valuable. © 2015 Wiley Periodicals, Inc.
TL;DR: In this paper, the first shell around the lithium ion is fully occupied with four ethylene carbonate (EC) molecules in both gas phase and solvent, and the contribution of vibration entropy to free energy of isomers of [Li(EC)n]+ reveals that the best candidates at zero-temperature cannot be maintained at finite temperatures due to the effects of their vibration entropy.
Abstract: The coordination and energetics of low-lying structures of [Li(EC)n]+ have been analyzed by density functional theory (DFT) and polarizable continuum model (PCM) at the B3LYP/6-311+G (d, p) level. The results show that the first shell around the lithium ion is fully occupied with four ethylene carbonate (EC) molecules in both gas phase and solvent. The examination on the contribution of vibration entropy to free energy of isomers of [Li(EC)n]+ reveals that the stability of the best candidates at zero-temperature cannot be maintained at finite temperatures due to the effects of their vibration entropy. In addition, structural transitions between the most stable four-coordinated and the metastable three-coordinated structure demand a very low energy barrier, suggesting that at a finite temperature the four-coordinated and three-coordinated isomers of [Li(EC)n]+ can coexist in the EC organic solvent lithium salt electrolyte. © 2015 Wiley Periodicals, Inc.
TL;DR: In this paper, a new approach for approximate obtaining the positively defined electronic kinetic energy density (KED) from electron density is described, which is presented as a sum of the Weizsacker KED, calculated in terms of electron density exactly, and unknown Pauli KED.
Abstract: This work describes a new approach for approximate obtaining the positively defined electronic kinetic energy density (KED) from electron density. KED is presented as a sum of the Weizsacker KED, which is calculated in terms of electron density exactly, and unknown Pauli KED. The latter is presented via local Pauli potential and Gritsenko–van Leeuwen–Baerends kinetic response potential, to which the second-order gradient expansion is applied. The resulting expression for KED contains only one empirical parameter. The approach allowed to correctly reproduce all the features of KED, and electron localization descriptors as electron localization function and phase-space defined Fisher information density for main types of bonds in molecules and molecular crystals. It is also demonstrated that the method is immediately applicable to derivation of mentioned bonding descriptors from experimental electron density. Herewith the method is significantly free from the drawback of Kirzhnits approximation, which is now commonly accepted for evaluation of the electronic kinetic energy characteristics from precise X-ray diffraction experiment. © 2015 Wiley Periodicals, Inc.
TL;DR: In this paper, the authors report accurate bond dissociation energies (BDEs) for a set of 18 molecules using the high-level W2 thermochemical protocol, and using this method, they have computed NBr BDEs for four widely used N-brominated compounds.
Abstract: Homolytic NBr bond dissociation constitutes the initial step of numerous reactions involving N-brominated species. However, little is known about the strength of NBr bonds toward homolytic cleavage. We herein report accurate bond dissociation energies (BDEs) for a set of 18 molecules using the high-level W2 thermochemical protocol. The BDEs (at 298 K) of the species in this set range from 162.2 kJ mol−1 (N-bromopyrrole) to 260.6 kJ mol−1 ((CHO)2NBr). In order to compute BDEs of larger systems, for which W2 theory is not applicable, we have benchmarked a wide range of more economical theoretical procedures. Of these, G3-B3 offers the best performance (root-mean-square deviations = 2.9 kJ mol−1), and using this method, we have computed NBr BDEs for four widely used N-brominated compounds. These include (BDEs are given in parentheses): N-bromosuccinimide (281.6), N-bromoglutarimide (263.2), N-bromophthalimide (274.7), and 1,3-dibromo-5,5-dimethylhydantoin (218.2 and 264.8 kJ mol−1). © 2015 Wiley Periodicals, Inc.
TL;DR: In this article, the authors present an overview on how density functional theory calculations can be used to design novel electrocatalytic materials for fuel cells, focusing the attention on non-metal doped graphene systems, which were reported to present excellent performances as electro catalysts for the oxygen reduction reaction at the cathodic electrode of fuel cells and are, thus, considered promising substitutes of platinum or platinum alloys electrodes.
Abstract: In this work, we present an overview on how density functional theory calculations can be used to design novel electrocatalytic materials for fuel cells. In particular, we focus the attention on non-metal doped graphene systems, which were reported to present excellent performances as electrocatalysts for the oxygen reduction reaction (ORR) at the cathodic electrode of fuel cells and are, thus, considered promising substitutes of platinum or platinum alloys electrodes. The methodology, originally proposed by Norskov et al. (J. Phys. Chem. B 2004, 108, 17886) for electrochemical processes at metal electrodes, is revisited and applied specifically to doped graphene. Finite molecular models of graphene are found to perform as well as periodic models for localized properties or reactions. Therefore, the sophisticated molecular quantum mechanics methodologies can be safely used to compute reliable Gibbs free energies of reaction in an aqueous environment for the various steps of reduction (at the cathode) or of oxidation (at the anode). Details of the reaction mechanisms and accurate cell onset- or over-potentials can be derived from the Gibbs free energy diagrams. The latter are computational quantities which can be directly compared to experimentally obtained cell overpotentials. Modeling electrocatalysis at fuel cells is, thus, an extremely powerful and convenient tool to improve our understanding of how fuel cells work and to design novel potentially active electrocatalytic materials. In this work, we present two specific applications of B-doped graphene, as electrocatalysts for the ORR at a half-cell cathode and for the methanol oxidation reaction (MOR) at a half-cell anode.
TL;DR: Using density functional theory (DFT) in conjunction with ultraviolet (UPS) and X-ray photoelectron spectroscopy (XPS), this article investigated a number of complexes and macromolecules and showed that the calculated Kohn-Sham energies of organic and metalorganic complexes can be used as approximate ionization energies.
Abstract: Using density functional theory (DFT) in conjunction with ultraviolet (UPS) and X-ray photoelectron spectroscopy (XPS), we investigated a number of complexes and macromolecules. We have shown on a large set of UPS, XPS, and DFT data that the calculated Kohn–Sham energies of organic and metalorganic complexes can be used as approximate ionization energies (IEs). It is possible to evaluate IEs with an accuracy of 0.1 eV with the density functional approximation (DFA) defect approach. This method has been successfully tested on a large number of boron β-diketonates and d-metal chelate and sandwich complexes. We interpreted the bands in the valence region of the XP spectra of macromolecular organosilicon compounds in the solid state by taking into account the density of states and the ionization cross-sections. According to DFT calculation results, the one-electron states in the valence region of the model compounds correlate with the positions of the spectral band maxima. © 2015 Wiley Periodicals, Inc.
TL;DR: In this article, the authors investigate the efficiency of Gaussian functions specifically designed for the description of the continuum proposed by Kaufmann et al. and assess the range of applicability of this approach by studying the hydrogen atom, i.e. the simplest atom for which exact calculations on a grid can be performed.
Abstract: We explore the computation of high-harmonic generation spectra by means of Gaussian basis sets in approaches propagating the time-dependent Schrodinger equation. We investigate the efficiency of Gaussian functions specifically designed for the description of the continuum proposed by Kaufmann et al. [J. Phys. B 22, 2223 (1989)]. We assess the range of applicability of this approach by studying the hydrogen atom, i.e. the simplest atom for which "exact" calculations on a grid can be performed. We notably study the effect of increasing the basis set cardinal number, the number of diffuse basis functions, and the number of Gaussian pseudo-continuum basis functions for various laser parameters. Our results show that the latter significantly improve the description of the low-lying continuum states, and provide a satisfactory agreement with grid calculations
for laser wavelengths λ0 = 800 and 1064 nm. The Kaufmann continuum functions therefore appear as a promising way of constructing Gaussian basis sets for studying molecular electron dynamics in strong laser fields using time-dependent quantum-chemistry approaches.
TL;DR: In this paper, the position and momentum space information densities of the Eckart potential are graphically demonstrated and their properties are studied, and it is shown that the Bialynicki-Birula and Mycielski inequality is saturated with increasing potential depth.
Abstract: In this work, the position and momentum space information densities of the Eckart potential are graphically demonstrated and their properties are studied. The position space information densities have quite an asymmetric shape depending on the values of quantum numbers. The information entropy is obtained and Bialynicki-Birula and Mycielski inequality is numerically saturated for some parameters of the potential. It is shown that the inequality is saturated with increasing potential depth.
TL;DR: In this paper, the authors discuss contemporary computational studies on the nature and strength of H-π, π-π and anion-π interactions and emphasize how modern quantum theoretical approaches ahead of experiment can provide insight into the design of new materials and devices by tuning the πinteractions in cooperative and competitive manners.
Abstract: The intermolecular and intramolecular noncovalent interactions involving π-aromatic compounds have attracted increasing attention over the last decades in chemistry, biology and material sciences. In this review, we discuss contemporary computational studies on the nature and strength of H-π, π-π, and anion-π interactions. We emphasize how modern quantum theoretical approaches ahead of experiment can provide insight into the design of new materials and devices by tuning the π-interactions in cooperative and competitive manners. Usefulness of such approaches towards designing new materials is demonstrated with some examples of molecular recognition/sensing, self-assembly/engineering, receptors, catalysts, supramolecules, graphene, and other two-dimensional (2D) materials/devices. © 2016 Wiley Periodicals, Inc.