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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.

Density functional theory (DFT) was used to study the structure, stability, and bonding in some selected neutral pentaatomic systems, viz., CGa2Ge2, CAlGaGe2, and CSiGa2Ge containing planar tetracoordinate carbon. The systems are kinetically stable, as predicted from the ab initio molecular dynamics simulations. The natural bond orbital (NBO) analysis showed that strong electron donation occurs to the central planar carbon atom by the peripheral atoms in all the studied systems. From the nucleus independent chemical shift (NICS) analysis, it is shown that the systems possess both σ- and π- aromaticity. The presence of 18 valence electrons in these systems, in their neutral form, appears to be important for their stability with planar geometries rather than tetrahedral structures. The nature of bonding is understood through the adaptive natural density partitioning analysis (AdNDP), quantum theory of atoms in molecules (QTAIM) analysis, and also via Wiberg bond index (WBI) and electron localization function (ELF).

This Review presents the current status of the noble gas (Ng)‐noble metal chemistry, which began in 1977 with the detection of AuNe+ through mass spectroscopy and then grew from 2000 onwards; currently, the field is in a somewhat matured state. On one side, modern quantum chemistry is very effective in providing important insights into the structure, stability, and barrier for the decomposition of Ng compounds and, as a result, a plethora of viable Ng compounds have been predicted. On the other hand. experimental achievement also goes beyond microscopic detection and characterization through spectroscopic techniques and crystal structures at ambient temperature; for example, (AuXe4)2+(Sb2F11 −)2 have also been obtained. The bonding between two noble elements of the periodic table can even reach the covalent limit. The relativistic effect makes gold a very special candidate to form a strong bond with Ng in comparison to copper and silver. Insertion compounds, which are metastable in nature, depending on their kinetic stability, display an even more fascinating bonding situation. The degree of covalency in Ng–M (M=noble metal) bonds of insertion compounds is far larger than that in non‐insertion compounds. In fact, in MNgCN (M=Cu, Ag, Au) molecules, the M−Ng and Ng−C bonds might be represented as classical 2c–2e σ bonds. Therefore, noble metals, particularly gold, provide the opportunity for experimental chemists to obtain sufficiently stable complexes with Ng at room temperature in order to characterize them by using experimental techniques and, with the intriguing bonding situation, to explore them with various computational tools from a theoretical perspective. This field is relatively young and, in the coming years, a lot of advancement is expected experimentally as well as theoretically.

A density functional theory-based computation has been carried out to reveal the geometrical and electronic structures of Mg2EP (1), where EP is an extended (3.1.3.1) porphyrinoid system. EP is a 2...

Noble gas can be no noble in certain situations from the perspective of structure, bonding, and reactivity. These situations could be extreme experimental conditions or others. In this contribution, we systematically investigate the impact of fullerene encapsulation on molecular structure and chemical reactivity of noble gas dimers (Ng2) in a few fullerene molecules. To that end, we consider He2, Ne2, and Ar2 dimers encapsulated in C50, C60, and C70 fullerenes. We unveil that bond distances of Ng2 inside fullerene become substantially smaller and noble gas atoms become more electrophilic. In return, these noble gas dimers make fullerene molecules more nucleophilic. Using analytical tools from density functional theory, conceptual density functional theory, and information-theoretic approach, we appreciate the nature and origin of these structure and reactivity changes. The results and conclusions from this work should provide more new insights from the viewpoint of changing the perspectives of noble gas reactivity.

This paper results from a round table discussion at the CCTC2018 Conference in Changsha City, Hunan, China, in December 2018. It presents a report on the status, prospects, and issues of conceptual density functional theory (CDFT). After a short exposition on the history of CDFT, its fundamentals, philosophy, and successes are highlighted. Then ten issues for reflection on the future of conceptual DFT are formulated and discussed, ending with one or more summarizing statements on the present status of various concepts/principles/practices and proposed directions for future research. The issues include the further analysis of the energy functional, E[N,v], extended to include effects of temperature, solvent, and mechanical forces, basic requirements for physically acceptable response functions as reactivity descriptors, the use of the grand canonical ensemble, the relevance of CDFT for chemical kinetics and thermodynamics, the domain of validity of CDFT-based principles, the combination of CDFT with reaction path calculations, information-theoretic descriptors, and the treatment of excited states and time dependence. The final issue advocates the transition of CDFT from an interpretative to a predictive mode; we believe this is of utmost importance for promoting CDFT as a viable alternative to wave function-based methods for the practicing chemist, a separate issue treated in the final section.

Density functional theory-based computations are carried out to analyze the electronic structure and stability of B2(MIC)2 complexes, where MIC is a mesoionic carbene, viz., imidazolin-4-ylidenes, pyrazolin-4-ylidene, 1,2,3-triazol-5-ylidene, tetrazol-5-ylidene, and isoxazol-4-ylidene. The structure, stability, and the nature of bonding of these complexes are further compared to those of the previously reported B2(NHC)2 and B2(cAAC)2. A thorough bonding analysis via natural bond order, molecular orbital, and energy decomposition analyses (EDA) in combination with natural orbital for chemical valence (NOCV) reveals that MICs are suitable ligands to stabilize B2 species in its (3)1∑g+ excited state, resulting in an effective B–B bond order of 3. Their high dissociation energy and endergonicity at 298 K for the dissociations L–BB–L → 2 B–L and L–BB–L → BB + 2 L (L = Ligand) indicate their viability at ambient condition. The donor property of MICs is comparable to that of NHCMe. The orbital interaction plays a greater role than the coulombic interaction in forming the B–L bonds. The EDA-NOCV results show that the sum of the orbital energies associated with the (+, +) and (+, −) L→[B2]←L σ-donations is far larger than that of L←[B2]→L π-back donation. It also reveals that cAACMe possesses the largest σ-donation and π-back donation abilities among the studied ligands, and the σ-donation and π-back donation abilities of MICs are comparable to those of NHCMe. Therefore, the present study shows that MICs would also be an excellent choice as ligands to experimentally realize new compounds having a strong B–B triple bond.

Particle Swarm Optimization (PSO), a population based technique for stochastic search in a multidimensional space, has so far been employed successfully for solving a variety of optimization problems including many multifaceted problems, where other popular methods like steepest descent, gradient descent, conjugate gradient, Newton method, etc. do not give satisfactory results. Herein, we propose a modified PSO algorithm for unbiased global minima search by integrating with density functional theory which turns out to be superior to the other evolutionary methods such as simulated annealing, basin hopping and genetic algorithm. The present PSO code combines evolutionary algorithm with a variational optimization technique through interfacing of PSO with the Gaussian software, where the latter is used for single point energy calculation in each iteration step of PSO. Pure carbon and carbon containing systems have been of great interest for several decades due to their important role in the evolution of life as well as wide applications in various research fields. Our study shows how arbitrary and randomly generated small Cn clusters (n = 3–6, 10) can be transformed into the corresponding global minimum structure. The detailed results signify that the proposed technique is quite promising in finding the best global solution for small population size clusters.

Department of Chemistry and Center for Theoretical Studies, Indian Institute of Technology Kharagpur, Kharagpur-721 302, West Bengal, India bDepartment of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400 076, India E-mail: pkc@chem.iitkgp.ac.in Manuscript received online 20 September 2018, accepted 30 September 2018 We have investigated the hydrogen storage potential of Li atom adsorbed and OLi2 functionalized (2,2) \(\gamma\)-graphyne nanotube (GNT), using density functional theory based calculations. We have found that Li atom prefers to stay on the trigonal pole (TP) of \(\gamma\)-GNT whereas OLi2 is strongly adsorbed on B atom of B, N-doped hexagonal ring site connected with acetylenic linkage, which is desirable for H2 storage. In presence of a small polar molecule OLi2 exploits the hydrogen storage ability more than that in the bare \(\gamma\)-GNT as well as the Li-adsorbed \(\gamma\)-GNT. The thermodynamical stability of hydrogen loaded \(\gamma\)- GNT is studied using binding energies, and change in reaction enthalpies. The maximum retrievable H2 uptake predicted that eight H2 molecules can be physically adsorbed in non-dissociated form per OLi2. The stability and reactivity of these hydrogen-adhered species are analyzed through the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). Exohedral CO sorption behaviour on Li-doped \(\gamma\)-GNT is also analyzed here

Ab initio and density functional theory-based computations are performed to investigate the structure and stability of H3SiNgNSi and HSiNgNSi compounds (Ng = Xe, Rn). They are thermochemically unstable with respect to the dissociation channel producing Ng and H3SiNSi or HSiNSi. However, they are kinetically stable with respect to this dissociation channel having activation free energy barriers of 19.3 and 23.3 kcal/mol for H3SiXeNSi and H3SiRnNSi, respectively, and 9.2 and 12.8 kcal/mol for HSiXeNSi and HSiRnNSi, respectively. The rest of the possible dissociation channels are endergonic in nature at room temperature for Rn analogues. However, one three-body dissociation channel for H3SiXeNSi and one two-body and one three-body dissociation channels for HSiXeNSi are slightly exergonic in nature at room temperature. They become endergonic at slightly lower temperature. The nature of bonding between Ng and Si/N is analyzed by natural bond order, electron density and energy decomposition analyses. Natural population analysis indicates that they could be best represented as (H3SiNg)+(NSi)− and (HSiNg)+(NSi)−. Energy decomposition analysis further reveals that the contribution from the orbital term (ΔEorb) is dominant (ca. 67%–75%) towards the total attraction energy associated with the Si-Ng bond, whereas the electrostatic term (ΔEelstat) contributes the maximum (ca. 66%–68%) for the same in the Ng–N bond, implying the covalent nature of the former bond and the ionic nature of the latter.

The global minimum structure of borospherene (B40) is a cage, comprising two hexagonal and four heptagonal rings. Born-Oppenheimer Molecular Dynamics simulations show that continuous conversions in between six and seven membered rings take place. The activation energy barrier for such a transformation is found to be 14.3 kcal·mol−1. The completely delocalized σ- and π-frameworks, as well as the conservation of the bonding pattern during rearrangement, facilitate the dynamical behavior of B40. B40 is predicted to act as a support-free spherical two-dimensional liquid at moderate temperature. In other words, B40 could be called as a nanobubble.

New porous three-dimensional metal-organic frameworks are synthesized that contain infinite chains of Srn and Ban rectangles. Their structures are elucidated by means of spectroscopic techniques such as nuclear magnetic resonance and Fourier transform infrared, and the respective crystal structures are determined. The electronic structure of basic units of the crystals are computed using density functional theory at the B3LYP/6-31G(d,p)/def2-TZVP level, and the bonding and reactivity are analyzed using natural bond orbital analysis, the quantum theory of atoms in molecules, and conceptual density functional theory. The possibilities of noble gas (Ng) storage inside the crystal structures are explored through modeling a Ng atom inside the frozen geometry of the crystal. It was found that a neon atom can fit into a cavity in the Sr and Ba crystal structures whereas other Ngs (He, Ar, Kr) exhibit repulsive interactions with the crystal structure. Ab initio molecular dynamics simulations for up to 500 fs at 77 and 298 K suggest that the structures incorporating a neon atom are kinetically stable. © 2015 Wiley Periodicals, Inc.

International audience; Before precipitating to form porphyry-type deposits, metals are transported and concentrated into magmas. Ultimately, they can enter crystalline phases or segregate into the volatile phase. In both cases, partition coefficients determine the partitioning according to the ambient physico-chemical conditions. Metal partitioning between the melt and the magmatic volatile phase (MVP) is driven by their solubility. In this study, Cu has been selected as a test for metal segregation. We evaluate qualitatively the metal's behavior with respect to the melt or to the MVP by comparing the difference in chemical potential and polarizability between the fluid phase and dissolved copper compound. Maps of polarizability are drawn after computing the chemical reactivity parameters (electrophilicity, hardness, and polarizability) for various silicate melts; a synthetic fluid phase with water, CO2, S18 compounds and halogens; and Cu-compounds as a test metal. Cu-compounds show a better affinity with the fluid phase, enhanced by the presence of S in its reduced form. It explains how Cu could segregate into the fluid phase at the magmatic stage before being enriched by diffusion or melt/vapor partitioning, leading to late hydrothermal precipitation. The method should therefore be considered as a model for understanding the behavior of other metals and their segregation during the magmatic stage.

Bonding, Reactivity and Aromaticity in Some Novel All-Metal Metallocenes

The multitopic pyrazine functionalized pro-ligand 2,6- bis ( N -methylimidazolium)pyrazinedichloride, L-1 ; 2,6- bis ( N -methylbenzimidazolium)pyrazinedichloride, L-2 and their respective Pd(II)–NHC complexes 1 and 2 have been synthesised and characterized by different spectroscopic methods and have been analyzed within a conceptual DFT framework. Single crystal X-ray structures of ( L-1 ) PF 6 and complex 1 have been determined. X-ray structure revels that 1 form a 12 member palladacycle. Both complex 1 and 2 , catalyse the Suzuki coupling reaction very well and from experimental and theoretical findings it is concluded that complex 1 is slightly catalytically more active than 2 .

Standard ab initio and density functional calculations are carried out to determine the structure, stability and reactivity of B 12 N 12 clusters with hydrogen doping. To lend additional support conceptual DFT based reactivity descriptors and the associated electronic structure principles are also used. Related cage aromaticity of this B 12 N 12 and nH 2 @B 12 N 12 are analyzed through the nucleus independent chemical shift values. Keywords: hydrogen storage; metal cluster; conceptual DFT; aromaticity (Published: 26 April 2011) Citation: Nano Reviews 2011, 2 : 5767 - DOI: 10.3402/nano.v2i0.5767

A new electronic structure principle, viz., the principle of electrophilicity equalization is proposed. An analytical justification as well as a numerical support for the same is provided., 9 pages, 2 tables

Novel NCN-pincer carbene complexes of Ru(II), 1,3-bis(2-pyridylmethyl)benzimidazolineruthenium(II) bishexafluorophosphate (2), and Pt(II), 1,3-bis(2-pyridylmethyl)benzimidazolinechloroplatinum(II) hexafluorophosphate (3), complexes based on 1,3-bis(2-pyridylmethyl)-1H-benzimidazolium chloride (1) were synthesized and characterized by different spectroscopic methods. Complex 2 shows an absorption maximum at 386 nm, blue-shifted in comparison to Ru(bpy)32+ and Ru(tpy)22+, probably due to the strong σ-donor and weak π-acceptor properties of the electron-rich NHC ligand. Electrochemical studies show Ru(II)/Ru(III) and Pt(II)/Pt(IV) reversible couples at 0.67 and 0.58 eV, respectively, lower than those for the analogous complexes of ligands like bipyridine (bpy), terpyridine (tpy) and phenylbipyridine (pbpy). The solid state structure of 2 was solved by X-ray diffraction. Theoretical studies (B3LYP/LANL2DZ) of the complex show a HOMO (−0.38594 au) mainly centered on the ruthenium and benzimidazole, whereas the LUMO (−0.25130 au) is populated by pyridines. Therefore, it is assumed that the charge transfer from HOMO → LUMO is mixed ILCT (interligand charge transfer)/MLCT (metal to ligand charge transfer). The observed lower redox potentials of the Pt(II) complex compared to the Ru(II) complex is supported by theoretically calculated ionisation potentials and also electron affinity values. To the best of our knowledge, 2 is the first example of a six-membered metallacycle homoleptic chelate pincer NCN–Ru(II) N-heterocyclic carbene complex.

This paper gives a critical account on the present status of the local hardness. We analyze the behavior of hardness related global, local, and nonlocal properties, paying particular attention to local hardness. Although this reactivity index has become very useful in predicting the regioselectivity of chemical reactions, the lack of a rigorous definition in the literature has shown that different approximations can yield different and sometimes contradictory conclusions. The present paper tries to provide insights into this controversial issue, starting from an approximate model of the hardness kernel and analyzing the features of the different models to evaluate the local and global hardnesses.

Some exact conditions for the extremals of the electrophilicity index, ω = μ(2)/2η (Parr, R. G.; von Szentpaly, L.; Liu, S. J. Am. Chem. Soc. 1999, 121, 1922), along an arbitrary reaction coordinate, have been carefully examined. Implications within the widely used finite difference approximation for the density-functional based reactivity descriptors, their relationship with the maximum hardness principle, and the reliability of the general relationships have been tested in the framework of computational evidence for some simple systems of chemical interest.

We present a density functional theory (DFT) study of the solvent effects on two intramolecular rearrangements. We have used relative values of energy, electronic chemical potential, chemical hardness and dipole polarizability as global descriptors to analyze the trans-N2H2→cis-N2H2 and F2S2→FSSF rearrangements in gas and solution phases. Our results agree well with the maximum hardness principle and the minimum polarizability principle. Both reactions become thermodynamically and kinetically more favorable, in the condensed phase. All the species associated with these reactions become less electrophilic in the presence of a polarizable environment. The lowering in the electrophilicity of the species upon solvation may be partitioned into two contributions. The first one contains the variations in electronic chemical potential for the change of phase; whereas the second one indirectly encompasses the variations in chemical hardness through the changes in the maximum charge transfer to the environment. For both reactions, the electronic chemical potential and chemical hardness variations cooperatively contribute to the loss in the electrophilicity power from the gas to solution phase.

Two intramolecular rearrangement reactions trans-N2H2 → cis-N2H2 and F2S2 → FSSF have been studied in both gas and solution phases using the ab initio SCF method at the Hartree−Fock level as well as using density functional theory with B3LYP exchange-correlation functionals with 6-311G** and 6-311++G** basis sets. Polarizability calculations have been performed using Sadlej's basis set also. Maximum hardness and minimum polarizability principles have been found to be valid in almost all cases. For the former reaction, the maximum molecular valency principle is obeyed. Reactions become more favorable, thermodynamically and kinetically, in the presence of the solvent. Variation of electrophilicity along the internal reaction coordinate is analyzed in terms of the profiles of the global electrophilicity index as well as condensed electrophilic Fukui functions at different atomic sites. It is found that electrophilicity decreases in the solution phase.

A thorough quantitative analysis of the HSAB principle is performed. Complex formation reactions of a typical soft acid, Ag+, and typical hard acid, HF, with the bases XH3 (X = N, P, As) are studied using the DFT/B3LYP method with the 6-311G** basis set. For the molecules containing Ag+ and As, corresponding pseudopotentials are used. Results of the calculations pertaining to the interactions of the hard acid, HF, are robust in comparison to those of Ag+. Correlation and nuclear relaxation effects are important in the case of the interactions of Ag+. Basis set superposition error changes the trend, and the results vary drastically with the quality of the basis set. Pseudopotentials do not introduce any error, and the zero-point energy represents at most 5% of the binding energy. The presence of the solvent, modeled as in Onsager's dipole method and in PCM, does not significantly change the trend. In the exchange reactions, both HSAB and maximum hardness principles are shown to be valid.