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1.
The electron density changes in molecular systems in the presence of external electric fields are modeled for simplicity in
terms of the induced charges and dipole moments at the individual atomic sites. A chemical potential equalisation scheme is
proposed for the calculation of these quantities and hence the dipole polarizability within the framework of density functional
theory based linear response theory. The resulting polarizability is expressed in terms of the contributions from individual
atoms in the molecule. A few illustrative numerical calculations are shown to predict the molecular polarizabilities in good
agreement with available results. The usefulness of the approach to the calculation of intermolecular interaction needed for
computer simulation is highlighted. 相似文献
2.
We employ Kato's theorem to prove that the electron interaction potential of Kohn–Sham density functional theory is finite at the nucleus of spherically symmetric and sphericalized atoms and ions. Therefore, this finiteness is a direct consequence of the electron–nucleus cusp condition for the density. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 79: 205–208, 2000 相似文献
3.
A. Trejo M. Calvino M. Cruz‐Irisson 《International journal of quantum chemistry》2010,110(13):2455-2461
The effect of the chemical surface passivation, with hydrogen atoms, on the energy band gap of porous cubic silicon carbide (PSiC) was investigated. The pores are modeled by means of the supercell technique, in which columns of Si and/or C atoms are removed along the [001] direction. Within this supercell model, morphology effects can be analyzed in detail. The electronic band structure is performed using the density functional theory based on the generalized gradient approximation. Two types of pores are studied: C‐rich and Si‐rich pores surface. The enlargement of energy band gap is greater in the C‐rich than Si‐rich pores surface. This supercell model emphasizes the interconnection between 3C‐SiC nanocrystals, delocalizing the electronic states. However, the results show a clear quantum confinement signature, which is contrasted with that of nanowire systems. The calculation shows a significant response to changes in surface passivation with hydrogen. The chemical tuning of the band gap opens the possibility plenty applications in nanotechnology. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2455–2461, 2010 相似文献
4.
The recently developed Asymptotic Density Model (ADM) [6, 9] is here implemented in the density functional framework using
the program deMon-KS [13]. While the original implementation divided the atoms into a core shell and a valence shell, the
present version allows for an arbitrary number of shells making it therefore more flexible and, as shown with benzene, potentially
more accurate. Moreover, since this method is derived through Poisson's equation, an expression for the electronic charge
density is also obtained. However, the present discussion will restrict itself to the electrostatic potential. Finally, even
though this method requires parametrization, it is shown that the parameters obtained for homonuclear diatomic species, and
used as is in molecular calculations, yield satisfactory results. Indeed, the ADM reproduces almost all basic features of
the MEP for all molecules presented here, (water, ammonia, ethylene, acetylene, hydrogen cyanide, carbon monoxide, benzene,
nitrous acid).
Received: 5 July 1996 / Accepted: 12 November, 1996 相似文献
5.
Ralph G. Pearson 《Theoretical chemistry accounts》1991,78(4):281-285
Summary An equation derived from density functional theory is used to improve energies calculated from approximate wave functions. The examples used are perturbed particle in a box and harmonic oscillators. The equation depends on the constancy of the chemical potential in these systems. The results are quite promising. 相似文献
6.
《Journal of computational chemistry》2017,38(28):2430-2438
Accurate computationally derived reduction potentials are important for catalyst design. In this contribution, relatively inexpensive density functional theory methods are evaluated for computing reduction potentials of a wide variety of organic, inorganic, and organometallic complexes. Astonishingly, SCRF single points on B3LYP optimized geometries with a reasonably small basis set/ECP combination works quite well‐‐B3LYP with the BS1 [modified‐LANL2DZ basis set/ECP (effective core potential) for metals, LANL2DZ(d,p) basis set/LANL2DZ ECP for heavy nonmetals (Si, P, S, Cl, and Br), and 6‐31G(d') for other elements (H, C, N, O, and F)] and implicit PCM solvation models, SMD (solvation model based on density) or IEFPCM (integral equation formalism polarizable continuum model with Bondi atomic radii and α = 1.1 reaction field correction factor). The IEFPCM‐Bondi‐B3LYP/BS1 methodology was found to be one of the least expensive and most accurate protocols, among six different density functionals tested (BP86, PBEPBE, B3LYP, B3P86, PBE0, and M06) with thirteen different basis sets (Pople split‐valence basis sets, correlation consistent basis sets, or Los Alamos National Laboratory ECP/basis sets) and four solvation models (SMD, IEFPCM, IPCM, and CPCM). The MAD (mean absolute deviation) values of SCRF‐B3LYP/BS1 of 49 studied species were 0.263 V for SMD and 0.233 V for IEFPCM‐Bondi; and the linear correlations had respectable R 2 values (R 2 = 0.94 for SMD and R 2 = 0.93 for IEFPCM‐Bondi). These methodologies demonstrate relatively reliable, convenient, and time‐saving functional/basis set/solvation model combinations in computing the reduction potentials of transition metal complexes with moderate accuracy. © 2017 Wiley Periodicals, Inc. 相似文献
7.
The exact Fermi potential yielding the Hartree–Fock electron density from orbital‐free density functional theory
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The exact expression for the Fermi potential yielding the Hartree–Fock electron density within an orbital‐free density functional formalism is derived. The Fermi potential, which is defined as that part of the potential that depends on the particles’ nature, is in this context given as the sum of the Pauli potential and the exchange potential. The exact exchange potential for an orbital‐free density functional formalism is shown to be the Slater potential. 相似文献
8.
9.
《Journal of Chemical Sciences》2005,117(5):525-531
The silicon atom may increase its coordination number to values greater than four, to form pentacoordinated compounds. It
has been observed experimentally that, in general, pentacoordinated compounds show greater reactivity than tetracoordinated
compounds. In this work, density functional theory is used to calculate the global softness and the condensed softness of
the silicon atom for SiH
n
F4−n
and SiH
n
F
5−n
1−
. The values obtained show that the global and condensed softness are greater in the pentacoordinated compounds than in the
tetracoordinated compounds, a result that explains the enhanced reactivity. If the results are analysed through a local version
of the hard and soft acids and bases principle, it is possible to suggest that in nucleophilic substitution reactions, soft
nucleophiles preferably react with SiH
n
F
5−n
1−
, and hard nucleophiles with SiH
n
F4−n
. 相似文献
10.
Fabrizio Santoro Vincenzo Barone Caterina Benzi Roberto Improta 《Theoretical chemistry accounts》2007,117(5-6):1073-1084
We review some recent advances in quantum mechanical methods devised specifically for the study of excited electronic state
of large size molecules in solution. The adopted theoretical/computational framework is rooted in the density functional theory
(DFT) and its time-dependent extension (TD-DFT) for the characterization of ground and excited states, in the polarizable
continuum model (PCM) for the treatment of bulk solvent effects, and in time-dependent quantum mechanical methods for chemical
dynamics. Selected applications to the simulation of absorption spectra, to the interpretation of time-resolved experiments,
and to the computation of dissociative electron transfer rates are presented and discussed. 相似文献
11.
12.
This article gives the details of the methodology used in constructing a symbolic algebra program designed for evaluating potentials as the functional derivatives of so-called functional generators in molecular density-functional theory. The derived formulae are used in illustrative examples involving partial functional integration, the comparison of the exchange potential arising from different mathematical representations of the electron density for a given functional generator, and the evaluation and comparison of the potential for different functional generators with a given density. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 300–307, 1998 相似文献
13.
Phase behavior and structural properties of homogeneous and inhomogeneous core-softened (CS) fluid consisting of particles interacting via the potential, which combines the hard-core repulsion and double attractive well interaction, are investigated. The vapour-liquid coexistence curves and critical points for various interaction ranges of the potential are determined by discrete molecular dynamics simulations to provide guidance for the choice of the bulk density and potential parameters for the study of homogeneous and inhomogeneous structures. Spatial correlations in the homogeneous CS system are studied by the Ornstein-Zernike integral equation in combination with the modified hypernetted chain (MHNC) approximation. The local structure of CS fluid subjected to diverse external fields maintaining the equilibrium with the bulk CS fluid are studied on the basis of a recently proposed third order+second order perturbation density functional approximation (DFA). The accuracy of DFA predictions is tested against the results of a grand canonical ensemble Monte Carlo simulation. Reasonable agreement between the results of both methods proves that the DFA theory applied in this work is a convenient theoretical tool for the investigation of the CS fluid, which is practically applicable for modeling numerous real systems. 相似文献
14.
Hsin‐Tsung Chen Jee‐Gong Chang Shin‐Pon Ju Hui‐Lung Chen 《Journal of computational chemistry》2010,31(2):258-265
We have elucidated the mechanism of CO oxidation catalyzed by gold nanoparticles through first‐principle density‐functional theory (DFT) calculations. Calculations on selected model show that the low‐coordinated Au atoms of the Au29 nanoparticle carry slightly negative charges, which enhance the O2 binding energy compared with the corresponding bulk surfaces. Two reaction pathways of the CO oxidation were considered: the Eley–Rideal (ER) and Langmuir–Hinshelwood (LH). The overall LH reaction O2(ads) + CO(gas) → O2(ads) + CO(ads) → OOCO(ads) → O(ads) + CO2(gas) is calculated to be exothermic by 3.72 eV; the potential energies of the two transition states ( TSLH1 and TSLH2 ) are smaller than the reactants, indicating that no net activation energy is required for this process. The CO oxidation via ER reaction Au29 + O2(gas) + CO(gas) → Au29–O2(ads) + CO(gas) → Au29–CO3(ads) → Au29–O(ads) + CO2(gas) requires an overall activation barrier of 0.19 eV, and the formation of Au29–CO3(ads) intermediate possesses high exothermicity of 4.33 eV, indicating that this process may compete with the LH mechanism. Thereafter, a second CO molecule can react with the remaining O atom via the ER mechanism with a very small barrier (0.03 eV). Our calculations suggest that the CO oxidation catalyzed by the Au29 nanoparticle is likely to occur at or even below room temperature. To gain insights into high‐catalytic activity of the gold nanoparticles, the interaction nature between adsorbate and substrate is also analyzed by the detailed electronic analysis. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
15.
以TZ2P为基组,采用Becke- Perdew(BP)等10种密度泛函分别对Ce(H2O)n3+(n=1~6)体系进行几何优化.运用绝对平均误差分析得出在所计算的10种密度泛函中Becke-PBEc为最优泛函.振动光谱分析表明,Ce(H2O)n3+(n=1~6)体系随着n增大,即H2O配位数的增加,Ce和O之间的相互作用越来越弱,O和H之间的相互作用越来越强,振动吸收频率与键长的呈现良好的线性关系.电子结构分析表明,f轨道的孤对电子不参与Ce—O之间的成键.热力学分析表明,Ce3+不易形成低配位的水合离子,但是在适当温度压强以及动力学条件下铈的低配位水合离子有可能实现转变. 相似文献
16.
The depletion potential between two colloid particles immersed in a hydrogen bonding fluid has been investigated by density functional theory. The study is motivated by the wide applications of hydrogen bonding fluids in the field of colloid science, and the effects of relevant factors on the depletion potential and depletion force between colloid particles have been studied. These factors include the size ratio of the colloid particle to the fluid molecule, the bulk density of the fluid, the functionality (the number of proton acceptors a and proton donors d) and hydrogen bonding strength as well as the colloid-fluid interaction energy. By comparing the depletion potential calculated under various conditions, it is shown that the effects of these factors on the depletion potential are very significant, and in particular in regulating the depletion force and its range. 相似文献
17.
Quantum chemical mass spectrometry: ab initio prediction of electron ionization mass spectra and identification of new fragmentation pathways
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Julie Cautereels Magda Claeys Davy Geldof Frank Blockhuys 《Journal of mass spectrometry : JMS》2016,51(8):602-614
The electron ionization mass spectra of four organic compounds are predicted based on the results of quantum chemical calculations at the DFT/B3LYP/6‐311 + G* level of theory. This prediction is performed ‘ab initio’, i.e. without any prior knowledge of the thermodynamics or kinetics of the reactions under consideration. Using a set of rules determining which routes will be followed, the fragmentation of the molecules' bonds and the complete resulting fragmentation pathways are studied. The most likely fragmentation pathways are identified based on calculated reaction energies ΔE when bond cleavage is considered and on activation energies ΔE? when rearrangements are taken into account; the final intensities of the peaks in the spectrum are estimated from these values. The main features observed in the experimental mass spectra are correctly predicted, as well as a number of minor peaks. In addition, the results of the calculations allow us to propose fragmentation pathways new to empirical mass spectrometry, which have been experimentally verified using tandem mass spectrometry measurements. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
18.
Ilya G. Ryabinkin Viktor N. Staroverov 《International journal of quantum chemistry》2013,113(11):1626-1632
The differential virial theorem (DVT) is an explicit relation between the electron density ρ( r ), the external potential, kinetic energy density tensor, and (for interacting electrons) the pair function. The time‐dependent generalization of this relation also involves the paramagnetic current density. We present a detailed unified derivation of all known variants of the DVT starting from a modified equation of motion for the current density. To emphasize the practical significance of the theorem for noninteracting electrons, we cast it in a form best suited for recovering the Kohn–Sham effective potential vs( r ) from a given electron density. The resulting expression contains only ρ( r ), vs( r ), kinetic energy density, and a new orbital‐dependent ingredient containing only occupied Kohn–Sham orbitals. Other possible applications of the theorem are also briefly discussed. © 2012 Wiley Periodicals, Inc. 相似文献
19.
Aziz Ghoufi Pierre Archirel Jean-Pierre Morel Nicole Morel-Desrosiers Anne Boutin Patrice Malfreyt 《Chemphyschem》2007,8(11):1648-1656
We report potential of mean force (PMF) calculations on the interaction between the p-sulfonatocalix[4]arene and a monovalent cation (Cs(+)). It has been recently shown from microcalorimetry and (133)Cs NMR experiments that the association with Cs(+) is governed by favourable cation-pi interactions and is characterized by the insertion of the cation into the cavity of the macrocycle. We show that the PMF calculation based upon a classical model is not able to reproduce both the thermodynamic properties of association and the insertion of the cation. In order to take into account the different contributions of the cation-pi interactions, we develop a new methodology consisting of changing the standard PMF by an additional contribution resulting from quantum calculations. The calculated thermodynamic properties of association are thus in line with the microcalorimetry and (133)Cs NMR experiments and the structure of the complex at the Gibbs free-energy minimum shows the insertion of the cation into the cavity of the calixarene. 相似文献
20.
Performance of heterogeneous computing with graphics processing unit and many integrated core for hartree potential calculations on a numerical grid
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Sunghwan Choi Oh‐Kyoung Kwon Jaewook Kim Woo Youn Kim 《Journal of computational chemistry》2016,37(24):2193-2201
We investigated the performance of heterogeneous computing with graphics processing units (GPUs) and many integrated core (MIC) with 20 CPU cores (20×CPU). As a practical example toward large scale electronic structure calculations using grid‐based methods, we evaluated the Hartree potentials of silver nanoparticles with various sizes (3.1, 3.7, 4.9, 6.1, and 6.9 nm) via a direct integral method supported by the sinc basis set. The so‐called work stealing scheduler was used for efficient heterogeneous computing via the balanced dynamic distribution of workloads between all processors on a given architecture without any prior information on their individual performances. 20×CPU + 1GPU was up to ~1.5 and ~3.1 times faster than 1GPU and 20×CPU, respectively. 20×CPU + 2GPU was ~4.3 times faster than 20×CPU. The performance enhancement by CPU + MIC was considerably lower than expected because of the large initialization overhead of MIC, although its theoretical performance is similar with that of CPU + GPU. © 2016 Wiley Periodicals, Inc. 相似文献