三硝基甲烷键离解能和生成焓的理论计算

采用密度泛函(DFT)四种交换/相关函数(B3LYP、B3P86、B3PW91和PBE0)结合不同的基函数,求得了三硝基甲烷C-NO2键的离解能(BDE),并且通过合理选择参考物硝基甲烷,设计等键等电子对反应,计算了气相三硝基甲烷分子的生成焓(HOF).与实验数据进行比较,PBE0/6-31g*计算出的BDE值最好,误差为-2.1 kcal mol-1;PBE0密度泛函结合带极化函数的6-31g基组得到的HOF值与实验值吻合的最好(误差在0.1 kcal mol-1以内).     

Modeling excitation properties of iridium complexes

Five iridium Ir(III) complexes have been studied using B3P86, B3LYP, M05, M06, M05‐2X, and M06‐2X functionals within configuration interaction singles (CIS) and time dependent density functional theory (TDDFT) formalisms with the aim of finding theory level that would allow for reliable prediction of emission properties. Knowledge of these properties prior to synthesis may significantly facilitate rational design of organic light‐emitting diodes (OLEDs). Our results indicate that the M05‐2X functional gives excellent results in this respect for the class of complexes studied here with the exception of the (bsn)₂Ir(acac) complex. We have shown that the discrepancy between the theoretical and experimental values for this complex is due to the presence of the sulfur atom. Copyright © 2009 John Wiley & Sons, Ltd.     

Use of ab initio methods to classify four existing energy density functionals according to their possible variational validity

Density functional theory is, of course, fundamentally a variational method. Therefore, in this Letter we suggest a classification of available energy density functionals into two groups, which we term (i) heuristic (H) and (ii) possibly variationally valid (PV). Quantum-chemical ab initio methods are employed on some selected neutral and anionic atomic systems and the molecules H₂O and LiOB to make this separation into H and PV groups in the case of the exchange-correlation functionals LDA, PBE, PW91 and B3LYP. This study shows that while the PBE is a potential candidate for being variationally valid, the B3LYP, today's other most widely used density functional, shows its strongly heuristic character. The investigation of variational validity can be an important part of systematic functional development, which is today's biggest challenge in DFT.     

Thirty years of density functional theory in computational chemistry: an overview and extensive assessment of 200 density functionals

In the past 30 years, Kohn–Sham density functional theory has emerged as the most popular electronic structure method in computational chemistry. To assess the ever-increasing number of approximate exchange-correlation functionals, this review benchmarks a total of 200 density functionals on a molecular database (MGCDB84) of nearly 5000 data points. The database employed, provided as Supplemental Data, is comprised of 84 data-sets and contains non-covalent interactions, isomerisation energies, thermochemistry, and barrier heights. In addition, the evolution of non-empirical and semi-empirical density functional design is reviewed, and guidelines are provided for the proper and effective use of density functionals. The most promising functional considered is ωB97M-V, a range-separated hybrid meta-GGA with VV10 nonlocal correlation, designed using a combinatorial approach. From the local GGAs, B97-D3, revPBE-D3, and BLYP-D3 are recommended, while from the local meta-GGAs, B97M-rV is the leading choice, followed by MS1-D3 and M06-L-D3. The best hybrid GGAs are ωB97X-V, ωB97X-D3, and ωB97X-D, while useful hybrid meta-GGAs (besides ωB97M-V) include ωM05-D, M06-2X-D3, and MN15. Ultimately, today's state-of-the-art functionals are close to achieving the level of accuracy desired for a broad range of chemical applications, and the principal remaining limitations are associated with systems that exhibit significant self-interaction/delocalisation errors and/or strong correlation effects.     

Quantum chemical study of a new class of sensitisers: influence of the substitution of aromatic rings on the properties of copper complexes

We present a computational study of new copper complexes with potential applications as sensitisers for solar cells. The applied methodology for this study is based on the density functional theory (DFT) and time-dependent DFT, using the B3LYP, PBE0 and M06 functionals with the LANL2DZ (D95V on first row), 6-31G(d,p), 6-311G(d,p) and DZVP basis sets. Optimised molecular structure, the absorption spectra, the molecular orbitals energies and the chemical reactivity parameters that arise from conceptual DFT were calculated. Solvent effects have been taken into account by an implicit approach, namely, the polarisable continuum model (PCM), using the non-equilibrium version of the integral equation formalism of the PCM model. Interesting work for experimentalists in the dye sensitised solar cells’ field.     

吉非替尼谱学性质计算研究

吉非替尼是第一个被批准上市用于治疗晚期非小细胞肺癌(NSCLC)的药物．该文采用5种密度泛函理论(DFT)方法B3LYP,BHandHLYP,M06-2X,CAM-B3LYP和LC-wPBE在6-311++G**水平上对吉非替尼分子的红外、紫外可见光谱及核磁共振谱进行了计算,并通过比较计算值和实验值得到最佳的计算条件．研究结果表明,CAM-B3LYP和M06-2X是最佳的用于描述吉非替尼分子红外光谱的方法;B3LYP//GIAO(Gauge-Including Atomic Orbital)方法预测得到的吉非替尼在(CH₃)₂SO中的¹H NMR与实验值最为接近,用于预测¹³C NMR的最佳方法是B3LYP//CSGT(Circularty Sgmmetrical Gabor Transform)．     

Role of electron correlation in the polydeprotonation of benzene to form trianions

Computations for anion, dianions, and trianions of benzene are carried out to study the role of electron correlation in the polydeprotonation of benzene leading to benzene trianions both in the singlet and triplet states. The computations, while assessing the use of polarization and diffuse functions, are performed with Møller–Plesset second‐order (MP2) perturbation theory and coupled‐cluster theory up to the level of CCSD(T)/6‐311++G(d,p)//MP2/6‐311++G(d,p), and with density functional theory (DFT) employing a hybrid, B3LYP, and a meta‐hybrid, M05‐2X, exchange‐correlation functionals with Gaussian basis set 6‐311++G(d,p) and correlation consistent basis set aug‐cc‐pVDZ. The deprotonation energies, including zero‐point energy correction, of benzene anion and dianions are found to be highly sensitive to the quantum mechanical method and the basis set used. The formation of dianions and trianions, where the anionic centers lie adjacent to each other, is observed with unusual behavior in the deprotonation energy and the geometrical parameters obtained from the different level of the theories. The two exchange‐correlation functionals compared show contrasting and unusual results for the trianionic species particularly for the triplet states, even if the diffuse functions are included in the basis set. Besides this, the ortho‐dianion and 1,3,5‐trianion are predicted to be ground‐state triplet at CCSD(T)/6‐311++G(d,p)//MP2/6‐311++G(d,p) and DFT/M05‐2X/6‐311++G(d,p) levels, whereas DFT/B3LYP/6‐311++G(d,p) predicts meta‐dianion and 1,2,3‐trianion to be ground‐state triplet where all the anionic centers lie adjacent to each other. Copyright © 2014 John Wiley & Sons, Ltd.     

Density functional theory and time‐dependent density functional theory study on a series of iridium complexes with tetraphenylimidodiphosphinate ligand

A series of heteroleptic cyclometalated Ir(III) complexes for organic light‐emitting diodes (OLEDs) application have been investigated theoretically to explore their electronic structures and spectroscopic properties. The geometries, the electronic structures, the lowest‐lying singlet absorptions and triplet emissions of Ir(dfppy)₂(tpip), Ir(tfmppy)₂(tpip), and theoretically designed models of Ir(ppy)₂(tpip) were investigated with the density functional theory (DFT)‐based approaches, where ppy = 2‐phenylpyridine, dfppy = 4,6‐difluorophenylpyridine, tfmppy = 4‐trifluoromethylphenylpyridine, and tpip = tetraphenylimidodiphosphinate. Their structures in the ground and their excited states have been optimized at the DFT/Becke 3‐parameter Lee Yang Parr (B3LYP)/Los Alamos National Laboratory 2‐double‐z (LANL2DZ) and time‐dependent DFT/B3LYP/LANL2DZ levels, and the lowest absorptions and emissions were evaluated at B3LYP and M062X level of theory, respectively. Furthermore, the energy transfer mechanism together with the advantage of low efficiency roll‐off for these complexes also can be analyzed here. Copyright © 2013 John Wiley & Sons, Ltd.     

Chemical reactivity of lithium‐doped fullerenes

The addition of free radicals and the 1,3 dipolar cycloaddition onto pristine and lithium‐doped C₆₀ were studied by means of the Perdew–Burke–Ernzerhof (PBE) and M06‐2X density functionals. In all cases, lithium increased the reactivity even though for the 1,3 dipolar cycloaddition onto C₆₀ the change observed with respect to bare C₆₀ was minimal. Both functionals employed gave similar encapsulation energies for Li@C₆₀ namely, 33.1 and 38.2 kcal/mol at the PBE/6‐31G* and M06‐2X/6‐31G*, respectively. However, the increased reactivity because of lithium doping determined at the PBE level is smaller as compared with that computed with the M06‐2X functional, whereas that determined at the second‐order Møller–Plesset (MP2) level is the largest one. For example, using the M06‐2X functional the binding energy of fluorine to Li@C₆₀ is 28.5 kcal/mol larger than that determined for C₆₀, whereas at the PBE/6‐31G* level it is predicted to be increased by 24.7 kcal/mol. The results clearly suggest that Li@C₆₀ is a much better free radical scavenger than C₆₀. Finally, the complex hindered rotations of lithium inside C₆₀ are expected to be strongly inhibited because lithium doping increases the well depth between the cage center and the equilibrium position near the addition site of the lithium atom. Copyright © 2011 John Wiley & Sons, Ltd.     

DFT and TD-DFT study on structure and properties of organic dye sensitizer TA-St-CA

The geometry, electronic structure, polarizability and hyperpolarizability of organic dye sensitizer TA-St-CA, which contains a π-conjugated oligo-phenylenevinylene unit with an electron donor–acceptor moiety, was studied using density functional theory (DFT), and the electronic absorption spectrum was investigated via time-dependent DFT (TD-DFT) with several hybrid functionals. The calculated geometry indicates that the strong conjugated effects are formed in the dye. The TD-DFT results show that the hybrid functional PBE1PBE and MPW1PW91 are more suitable than B3LYP for calculating electronic absorption spectra. The features of electronic absorption spectra were assigned on account of the qualitative agreement between the experiment and the calculations. The absorption bands in visible and near-UV region are related to photoinduced electron transfer processes, and the diphenylaniline group is major chromophore that contributed to the sensitization, and the interfacial electron transfer are electron injection processes from the excited dyes to the semiconductor conduction band. Compared with the similar dye D5, the good performance of TA-St-CA in dye-sensitized solar cells may be resulted from the higher energy level of the lowest unoccupied molecular orbital and the larger oscillator strengths for the most excited states with intramolecular electron transfer character.     

Understanding the absorption and emission spectra of borondipyrromethene dye and its substituted analogues

Borondipyrromethene (BODIPY) dye possesses a bright and long wavelength emitting fluorescent character with a wide spectral range from visible to near infrared region. In the present work, the spectral properties of BODIPY dyes were analyzed using ab intio and density functional theory methods. The ground and excited state geometries of BODIPY and its substituted analogues in chloroform medium, were optimized using the density functional theory (DFT) and singly excited configuration interaction (CIS) methods. Based on the ground and excited state geometries, the absorption and emission spectra have been calculated using time-dependent density functional theory (TDDFT) method. The TDDFT calculations have been performed using hybrid exchange correlation functionals B3LYP and M06-HF and long-range separated functionals LC-BLYP, LC-BOP, LC-PBE, LC-PBE0 and CAM-B3LYP. The solvent phase calculations were carried out using polarizable continuum model (PCM). The TDDFT investigation reveals that the substitution of acceptor, donor–donor, donor–acceptor–donor and phenyl group in BODIPY dye influence the absorption and emission spectra significantly.     

Quantum Monte Carlo assessment of density functionals for π-electron molecules: ethylene and bifuran

ABSTRACT

We perform all-electron, pure-sampling quantum Monte Carlo (QMC) calculations on ethylene and bifuran molecules. The orbitals used for importance sampling with a single Slater determinant are generated from Hartree-Fock and density functional theory (DFT). Their fixed-node energy provides an upper bound to the exact energy. The best performing density functionals for ethylene are BP86 and M06, which account for 99% of the electron correlation energy. Sampling from the π-electron distribution with these orbitals yields a quadrupole moment comparable to coupled cluster CCSD(T) calculations. However, these, and all other density functionals, fail to agree with CCSD(T) while sampling from electron density in the plane of the molecule. For bifuran, as well as ethylene, a correlation is seen between the fixed-node energy and deviance of the QMC quadrupole moment estimates from those calculated by DFT. This suggests that proximity of DFT and QMC densities correlates with the quality of the exchange nodes of the DFT wave function for both systems.     

Gas-phase doubly charged complexes of cyclic peptides with copper in +1, +2 and +3 formal oxidation states: formation, structures and electron capture dissociation

Copper complexes with a cyclic D-His-β-Ala-L-His-L-Lys and all-L-His-β-Ala-His-Lys peptides were generated by electrospray which were doubly charged ions that had different formal oxidation states of Cu(I), Cu(II) and Cu(III) and different protonation states of the peptide ligands. Electron capture dissociation showed no substantial differences between the D-His and L-His complexes. All complexes underwent peptide cross-ring cleavages upon electron capture. The modes of ring cleavage depended on the formal oxidation state of the Cu ion and peptide protonation. Density functional theory (DFT) calculations, using the B3LYP with an effective core potential at Cu and M06-2X functionals, identified several precursor ion structures in which the Cu ion was threecoordinated to pentacoordinated by the His and Lys side-chain groups and the peptide amide or enolimine groups. The electronic structure of the formally Cu(III) complexes pointed to an effective Cu(I) oxidation state with the other charge residing in the peptide ligand. The relative energies of isomeric complexes of the [Cu(c-HAHK + H)](2+) and [Cu(c-HAHK - H)](2+) type with closed electronic shells followed similar orders when treated by the B3LYP and M06-2X functionals. Large differences between relative energies calculated by these methods were obtained for open-shell complexes of the [Cu(c-HAHK)](2+) type. Charge reduction resulted in lowering the coordination numbers for some Cu complexes that depended on the singlet or triplet spin state being formed. For [Cu(c-HAHK - H)](2+) complexes, solution H/D exchange involved only the N-H protons, resulting in the exchange of up to seven protons, as established by ultra-high mass resolution measurements. Contrasting the experiments, DFT calculations found the lowest energy structures for the gas-phase ions that were deprotonated at the peptide C(α) positions.     

Analysis of indolylfulgide spectral properties using time dependent density functional theory

An analysis of absorbance maxima of 10 indolylfulgides (open and closed isomeric forms) by time-dependent density functional theory (TD-DFT) is presented. Ground state structures were examined using density functional theory (DFT), using five different functionals. TD-DFT was applied to each structure using four different functionals and the theoretical calculations were compared to experimental data. Comparison of these data was used to determine which functional best describes the ground and excitation energies of the investigated indolylfulgides. Overall we found that by using TD-M06//M06, the vertical excitation energy could be determined within ±0.058 eV (±11 nm).     

Quantum chemical calculations of bond dissociation energies for COOH scission and electronic structure in some acids

Quantum chemical calculations are performed to investigate the equilibrium C-COOH bond distances and the bond dissociation energies(BDEs) for 15 acids.These compounds are studied by utilizing the hybrid density functional theory(DFT)(B3LYP,B3PW91,B3P86,PBE1PBE) and the complete basis set(CBS-Q) method in conjunction with the 6311G** basis as DFT methods have been found to have low basis sets sensitivity for small and medium molecules in our previous work.Comparisons between the computational results and the experimental values reveal that CBS-Q method,which can produce reasonable BDEs for some systems in our previous work,seems unable to predict accurate BDEs here.However,the B3P86 calculated results accord very well with the experimental values,within an average absolute error of 2.3 kcal/mol.Thus,B3P86 method is suitable for computing the reliable BDEs of C-COOH bond for carboxylic acid compounds.In addition,the energy gaps between the highest occupied molecular orbital(HOMO) and the lowest unoccupied molecular orbital(LUMO) of studied compounds are estimated,based on which the relative thermal stabilities of the studied acids are also discussed.     

Density functional theory study on the magnetic properties of Co3O4 with normal spinel structure

The magnetic properties of Co₃O₄ with a normal spinel structure were investigated via the full potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). The exchange and correlation effects between electrons were treated with a standard generalized gradient approximation (GGA) from Perdew–Burke–Ernzerhof (PBE), as a function of the on-site Coulomb U term, the GGA−PBE+U method, and a B3PW91 hybrid functional with different Hartree–Fock exchange admixtures. Were calculated all of these exchange–correlation (XC) functionals both with and without spin–orbit coupling (SOC). The objective for these calculations was to predict the ground-state magnetic structure of Co₃O₄ crystal using different XC functionals and to investigate the influence that SOC had on these results. All of our calculations confirmed that the collinear antiferromagnetic (AFM) order was energetically more favorable than the ferromagnetic (FM) one, which agrees with experimental findings. This conclusion was not influenced by the XC functional type employed or whether the spin–orbit effect was used. Thus, the present work does not confirm the recent DFT plane wave pseudopotential results that when including spin–orbit effects, the calculations determined that the collinear FM state had lower energy than the AFM one.     

The mechanism of the gas-phase elimination kinetics of the β,γ-unsaturated aldehyde 2,2–dimethyl-3-butenal: a theoretical study

The study on the mechanism of the gas-phase elimination or thermal decomposition kinetics of 2, 2-dimethyl-3-butenal has been carried out by using theoretical calculation at MP2, combined ab initio CBSQB3 and DFT (B3LYP, B3PW91, MPW1PW91, PBEPBE, PBE1PBE, CAMB3LYP, M06, B97d) levels of theory. A good reasonable agreement between experimental and calculated parameters was obtained by using CAMB3LYP/6-311G(d,pd) calculations. The contrasted calculated parameters against experimental values suggested decarbonylation reaction to proceed through a concerted five-membered cyclic transition state type of mechanism, involving the hydrogen transfer from the carbonyl carbon to the gamma carbon, consistent with observed kinetic isotope effect. The breaking of alpha carbon–carbonyl carbon bond to produce carbon monoxide is 50% advanced in the transition state. The reaction mechanism may be described as a concerted moderately non-synchronous process. Examination of the Atoms in Molecules (AIM) analysis of electron density supports the suggested mechanism.     

Benchmark CCSD(T) and DFT study of binding energies in Be7 − 12: in search of reliable DFT functional for beryllium clusters

We present a computational study of the stability of small homonuclear beryllium clusters Be_{7 ? 12} in singlet electronic states. Our predictions are based on highly correlated CCSD(T) coupled cluster calculations. Basis set convergence towards the complete basis set limit as well as the role of the 1s core electron correlation are carefully examined. Our CCSD(T) data for binding energies of Be_{7 ? 12} clusters serve as a benchmark for performance assessment of several density functional theory (DFT) methods frequently used in beryllium cluster chemistry. We observe that, from Be₁₀ clusters on, the deviation from CCSD(T) benchmarks is stable with respect to size, and fluctuating within 0.02 eV error bar for most examined functionals. This opens up the possibility of scaling the DFT binding energies for large Be clusters using CCSD(T) benchmark values for smaller clusters. We also tried to find analogies between the performance of DFT functionals for Be clusters and for the valence-isoelectronic Mg clusters investigated recently in Truhlar's group. We conclude that it is difficult to find DFT functionals that perform reasonably well for both beryllium and magnesium clusters. Out of 12 functionals examined, only the M06-2X functional gives reasonably accurate and balanced binding energies for both Be and Mg clusters.