Basis Set Superposition Error Research Articles

Reproduction of experimental data for stacked caffeine dimers using various computational methods

Reliable description of stacking interaction of aromatic molecules is important for the understanding structure, stability, and functions of biopolymers. The caffeine molecule is an ideal object for this study as the stacking interactions are the preferential ones for self-associations of this hydrophobic molecule without H-bond donor groups. The analysis of anhydrous caffeine crystal structures revealed five types of caffeine stacking dimers. Geometry optimization of these dimers was performed using two molecular mechanics force fields, ab-initio method Møller Plesset of the second order (MP2), and density functional theory (DFT) with different functionals. The comparison of geometric parameters of the caffeine dimers obtained using different theoretical methods with those in crystals enables us to suggest the methods providing the most reliable stacking characteristics. These methods are: the MP2 with Basis Set Superposition Error correction (MP2/CP), Poltev force field, along with PBE0-DH, SCAN and PBE-D3 functionals of DFT. For the methods, which give the dimer interaction energy close to that obtained by MP2/CP method, the evaluated sublimation enthalpy values are shown to be close to the experimental data. Additionally, MP2/CP, Poltev FF and PBE0-DH functional showed to be the methods that describe well both the energy and geometry of the caffeine stacking dimer.

HF Trimer: A New Full-Dimensional Potential Energy Surface and Rigorous 12D Quantum Calculations of Vibrational States.

HF trimer, as the smallest and the lightest cyclic hydrogen-bonded (HB) cluster, has long been a favorite prototype system for spectroscopic and theoretical investigations of the structure, energetics, spectroscopy, and dynamics of hydrogen-bond networks. Recently, rigorous quantum 12D calculations of the coupled intra- and intermolecular vibrations of this fundamental HB trimer (J. Chem. Phys. 2023, 158, 234109) were performed, employing an older ab initio-based many-body potential energy surface (PES). While the theoretical results were found to be in reasonably good agreement with the available spectroscopic data, it was also evident that it is highly desirable to develop a more accurate 12D PES of HF trimer. Motivated by this, here we report a new, and the first fully ab initio 12D PES of this paradigmatic system. Approximately 42,540 geometries were sampled and calculated at the level of CCSD(T)-F12a/AVTZ. The permutationally invariant polynomial-neural network based Δ-machine learning approach (J. Phys. Chem. Lett. 2022, 13, 4729) was employed to perform cost-efficient calculations of the basis-set-superposition error (BSSE) correction. By strategically selecting data points, this approach facilitated the construction of a high-precision PES with BSSE correction, while requiring only a minimal number of BSSE value computations. The fitting error of the final PES is only 0.035 kcal/mol. To assess its performance, the 12D fully coupled quantum calculations of excited intra- and intermolecular vibrational states of HF trimer are carried out using the rigorous methodology developed by us earlier. The results are found to be in a significantly better agreement with the available spectroscopic data than those obtained with the previously existing semiempirical 12D PES.

Computational Exploration of the Impact of Low‐Spin and High‐Spin Ground State on the Chelating Ability of Dimethylglyoxime Ligand on Dihalo Transition Metal: A QTAIM, EDA, and CDA Analysis

ABSTRACTWe have explored the chelation of dimethylglyoxime ligand to divalent (ndx: x = 6, 7, 8) transition metal (TM) cations in two media (gas phase and water) at the B3LYP//LANL2DZ/6–311+G (d,p) and B3LYP/def2‐TZVP level at lower multiplicity and higher multiplicity states. Majority of the 18 optimized halide (chloride and bromide) complexes prefer square planar configuration. The correlations discerned between the experimental structural data and their estimated counterparts demonstrate a good credibility for complexes at lower multiplicity state. The basis set superposition errors (BSSEs) estimated is very small which reflects the fact that the choice of different basis sets (B3LYP//LANL2DZ/6–311+G (d,p)) introduces a slight bias in the calculation of energies. The ADMP (atom‐centered density matrix propagation) simulations in water on chloride complexes indicate the irreversible nature of these M—N dissociation in trajectory simulation process. This fact explains our exclusive focus on the examination of the [glyoxime ligand]…[MX2] interactions. In addition, the solvation of (3d and 4d) transition metal chloride complexes causes a sensitive augmentation of the metal ion affinity (MIA) with an average of 0.29 and 0.24 kcal/mol. In both multiplicity states, the topological parameters have illustrated that the M—N and M—X bonds are typical metal–ligand in both media. The average ΔEorb/ΔEsteric ratio equal to 0.45 and 0.11 in gas phase and water, respectively, reveals the predominance of the contributions from non‐covalent bonding interactions (NCI) compared to those of covalent bonding. But, the maximal value equal to 6.760 is obtained for bromide rhodium complex in water. NBO analysis in both media highlights the fact that a more pronounced ionic character is observed for the majority of the chloride complexes at both spin multiplicity states because of their higher retained charges on the metal atom. For [dimethylglyoxime]…[MX2] interaction (X = Cl and Br), the charge decomposition analysis demonstrates that the lowest value of the d/b ratio is found for the chloride platinum complex at lower multiplicity state in water. This is a proof of its strong relativistic effects.

The Quality of Embedding Charges Is Critical for Convergence of Many-Body Expansions When BSSE Is Absent.

There is conflicting evidence in the literature concerning the benefits of charge embedding on the convergence of many-body expansions (MBEs). Using a systematic series of water and ion-water clusters of varying size, this study indicates that the effects of charge embedding can be masked by basis set superposition error (BSSE). When BSSE is removed, this study demonstrates that charge embedding can significantly accelerate MBE convergence, where the electrostatically embedded two-body method, EE-MBE(2), can often yield accuracy close to the four-body method, MBE(4). Contrary to previous studies on smaller systems, this work shows that the performance of EE-MBE is highly sensitive to the charge model, with the best performance obtained when the natural population analysis (NPA) charge model is used and generated at the same level of theory used in the subsystem and supersystem calculations. It was demonstrated that the "3c" composite method, PBEh-3c, yields NPA atomic charges that are in excellent agreement with those obtained from supersystem density functional theory calculations. The linear-scaling X-Polarization method provides a more general approach to estimating these supersystem QM atomic charges, but its performance depends on how the fragments are defined.

Evaluating interaction energy versus electron density relationships to estimate inter and intramolecular H-bonding

We investigate the computational effects on the relationships between interaction energy (ΔE) and electron density (ρ), at the critical point obtained from 19 intermolecular H-bonded dimers, to estimate inter and intramolecular interactions of larger H-bonded systems. Our analysis examines basis set superposition error (BSSE) effects, dispersion energy corrections, and the exchange-correlation energy model on the ΔE vs. ρ linear regressions. The calculations were carried out within density functional theory (DFT) combined with the 6-31+G(d,p) and def2-TZVPP basis sets. This procedure quantifies the average effects of BSSE for different levels of approximation, and underscore the sensitivity of the ΔE estimation together with dispersion corrections. This is valuable for the development of DFT-based estimators of multiple interaction energies of large H-bonded systems with low computational cost. We have applied this procedure by analyzing H-bonded biological molecules, such as DNA base pairs, an asparagine side chain, and an AZT molecule. Our estimated H-bond interaction energies are in agreement with previous studies, and emphasize the importance of methodological considerations for accurately predicting interaction energies using DFT combined with topological parameters.

Quantitative evaluation of noncovalent interactions with negative fragmentation approach including basis set superposition error correction

Abstract We propose a negative fragmentation approach (NFA), including counterpoise (CP) correction to basis set superposition error (BSSE) for quantitatively evaluating intra- and intermolecular noncovalent interactions. Noncovalent interactions are widely found in chemistry and biology and are regarded as essential interactions. However, there are few general methods for evaluating these individual intra- and intermolecular interaction energies because of two issues: (i) difficulty in the evaluation of intramolecular interactions due to the interacting sites connected with covalent bonds and (ii) BSSE affecting the quantitative accuracy of interaction analysis. In our scheme, we overcome the issue (i) using the NFA scheme, which can evaluate intra- and intermolecular interactions as a fragment–fragment interaction of interacting sites, and address the issue (ii) using the CP method. Here, NFA including the CP correction was applied to various molecular systems, providing comparable results for intermolecular interactions to supermolecule calculations with the CP correction and also succeeding in the evaluation of intramolecular interactions and its BSSEs. It is notable that our NFA scheme does not require any particular program or a modification of the program codes. These indicate that many researchers can apply our NFA scheme to various molecular systems.

Basis Set Extrapolation from the Vanishing Counterpoise Correction Condition.

Basis set extrapolations are typically rationalized either from analytical arguments involving the partial-wave or principal expansions of the correlation energy in helium-like systems or from fitting extrapolation parameters to reference energetics for a small(ish) training set. Seeking to avoid both, we explore a third alternative: extracting extrapolation parameters from the requirement that the BSSE (basis set superposition error) should vanish at the complete basis set limit. We find this to be a viable approach provided that the underlying basis sets are not too small and reasonably well balanced. For basis sets not augmented by diffuse functions, BSSE minimization and energy fitting yield quite similar parameters.

Synthesis, QTAIM, anticancer activity analysis of pyrrole-imidazole/benzimidazole derivatives and investigation of their reactivity properties using DFT calculations and molecular docking

As part of our ongoing investigation into pyrrole derivatives, we here present the synthesis, spectroscopic characterization, QTAIM, reactivity, anticancer activity, and comparative experimental and computational analysis of pyrrole-imidazole ((3l), (3p)) and benzimidazole derivatives ((3h), (3i), (3j), (3k), (3m), (3n), (3o)). All synthesized compounds (3h-3p) have been well characterized by spectroscopic techniques (FT-IR, 1H and 13C NMR, Mass spectrometry). The experimental 1H and 13C NMR chemical shift values of synthesized pyrrole-imidazole (3l, 3p) and benzimidazole (3h-3o) derivatives have been well corroborated with computed chemical shifts. The vibrational analysis for four derivatives of pyrrole-benzimidazole (3m), (3n), (3o), and pyrrole-imidazole (3p) has the suitability for dimer formation in solid state by intermolecular heteronuclear hydrogen bonding (N–H···O) and the interaction energy of dimers are calculated to be 10.88, 11.70, 9.89 and 10.72 kcal/mol, using DFT. After basis-set superposition error (BSSE) correction, the interaction energies of dimers were found to be 11.12, 12.11, 10.13, and 11.52 kcal/mol. Estimated intermolecular H-bond in (3m-3n) compounds were found to be -13.38, -12.86, -11.02, and -11.28 kJ/mol using QTAIM. All the synthetic pyrrole-imidazole (3l, 3p) and benzimidazole (3h-3o) derivatives exhibit strong antileukemia activity in vitro against the proliferative cell line L1210 leukemia cells. A dataset of investigated compounds was subjected for molecular modelling simulation against three distinct proteins (SYK, PI3K, and BTK), which was found to be highly implicated in the favourable interaction between the compounds and their target proteins in every instance. The synthesized pyrrole-imidazole (3l, 3p) and benzimidazole (3h-3o) derivatives shown favourable interactions with their target proteins, with high activity and binding free energy values falling between 15.22 and 13.43 and -7.4 and -9.8 kcal/mol, respectively. The structure of pyrrole-imidazole (3l, 3p) and benzimidazole (3h-3o) derivatives is thoroughly examined, and several parameters are proposed here to improve their anticancer activity.

A benchmark quantum chemical probe into the structural stability of various anchoring groups to form graphene oxides

Graphene and graphene oxides (GO) are among the intriguing materials of this era, being widely used in many modern technologies. Many properties of GOs are owing to its more reactivity as compared with graphene. It is interesting to study the changes in chemical properties while changing graphene to GOs. There are commonly known three ways to change a graphene to GO by adding epoxy, hydroxyl and carboxyl groups. We used quantum chemical methods to systematically attach epoxy, hydroxyl and carboxyl groups on graphene surface. We designed GOs as hydroxyl (OH-GO), epoxy (O-GO), carboxyl (COOH-GO) derivatives of graphene and one derivative with all functional groups collectively (HEC-GO). In the current work, we have employed DFT method by using B3LYP functional along with 6-31G* basis set to calculate electronic properties computationally. The calculated band gap for GOs are less than pristine graphene (1.680 eV). Minimum band gap of 1.565 eV is shown by O-GO, while compound HEC-GO with collective functional groups shows 1.539 eV. Frontier molecular orbitals, molecular electrostatic potential maps and density of state analysis has been performed. Localized orbital locator (LOL) are drawn to check the charge transfer via topology visualization. Binding energy has been calculated using basis set superposition error (BSSE) correction. COOH-GO shows binding energy of −302.90 kcal/mol which is seen better than OH-GO and O-GO systems. NPA analysis showed that there is more ICT as functional groups are attached to the pristine graphene molecule because of the strong electron withdrawing nature of attached groups. TD-DFT with TD-B3LYP/6-31G* is employed to check the absorption properties of entitled compounds. Graphene shows maximum absorption at 341 nm, while GOs shows red shift, e.g., COOH-GO at 371 nm, OH-GO at 386 nm, HEC-GO at 409 nm and O-GO at 462 nm. The current investigation highlighted the molecular level insights about the stability and relative role of epoxy, hydroxyl and carboxyl groups on graphene surface during formation of GOs.

Computer simulation‐guided template selection for a molecularly imprinted polymer for selective trifluralin adsorption

AbstractTo meet selective adsorption toward trifluralin, a novel molecularly imprinted polymer (MIP) was fabricated by the dummy template molecular imprinting technology. First, computational simulation was performed to select a suitable dummy template, 3,5‐dinitro‐4‐methylbenzoic acid (T1), based on the maximum basis set superposition error (BSSE)‐corrected binding interaction energy (ΔE) of the monomer N‐vinylpyrrolidone (NVP)‐T1 complex and its structural overlap with trifluralin. Then, the MIP was prepared via the bulk polymerization. The adsorption experiments showed the MIP exhibited a trifluralin adsorption capacity of 5.1 mg g−1, an imprinting factor (IF) of 2.2, and short adsorption equilibrium time of 5 min. The adsorption of trifluralin conformed to the Freundlich adsorption (R2 = 0.985) and pseudo‐second‐order model (R2 = 0.999). In addition, the MIP exhibited selectivity to trifluralin over other adsorbents, including structural analogs (pendimethalin and oryzalin), pesticide (carbendazim), and nitrocompounds (nitrofurantoin, furazolidone, and furaltadone), with the selectivity factor (β) in the range of 1.2–3.0, respectively. In trifluralin/oryzalin mixture, the IF toward oryzalin was still as high as 1.9. The removal rate of the MIP to trifluralin in environmental water samples ranged from 90.08% to 99.04%. This study provides theoretical and experimental insights for the preparation of MIP using dummy templates.

Insights into the electronic structure and interaction energies of 4-ethoxy-N-(4-ethoxy-2-hydoxybenzylidene)benzohydrazide

The molecule 4-ethoxy-N-(4-ethoxy-2-hydroxybenzylidene)benzohydrazide (4EHB) is characterized by a rigid aroylhydrazone core, acting as a mesogenic unit, and a flexible chain at its terminal end. The aroylhydrazone core comprises two aromatic rings linked by connecting groups, resulting in moderate size and elongation of the molecule. Variations in the positions and orientations of elongated molecules give rise to different mesogenic phases such as Nematic, Smectic, and Hexatic Smectic. The mesogenic behavior of aroylhydrazone-based materials is governed by various non-covalent interactions. In this study, molecular geometry optimization, analysis of HOMO-LUMO orbitals, and MEP surfaces of individual and pairs of 4EHB molecules were conducted using the Density functional B3LYP technique with the basis set 6-31G**. Intermolecular interaction energies between pairs of 4EHB molecules are evaluated using the technique M06-2X/6-311G** in stacking, terminal, and side-to-side (in-plane) configurations. Basis set superposition error (BSSE) is corrected using counterpoise method and interaction energy(I.E.) is decomposed in different components using SAPT0 method at level 6-311G**, which provided insights into the mesogenic behavior of the system.

Stone-Wales defective C60 fullerene for hydrogen storage

Hydrogen energy is one of promising non-polluting and renewable energy sources. In this paper, we present a first principal study of hydrogen storage in pure C60 fullerene cage and Stone-Wales (SW) defective C60 cages using density functional theory (DFT) with applying both the exchange functional B3LYP and the dispersion correction wb97xd at 6–31+g(d,2p) basis set. In addition, the counterpoise correction is applied, and the basis set superposition error is calculated. The calculations underscore that the hydrogenation binding energy of C60 cages occurs through an endothermal process for C60Hin with a hydrogen binding energy of 0.09 eV and through an exothermal process for C60Hout, C60SW66Hout, and C60SW65Hout, cages with hydrogen binding energies of −2.17 eV, −2.96 eV, and −2.20 eV, respectively. Remarkably, for the first time, the intermediate hydrogen binding energy is found inside C60SW66Hin fullerene, and C60SW65Hin fullerene cages with energies of −0.26 eV and −0.81 eV, respectively. The hydrogen adsorption inside the cavity of C60SW66 fullerene cage is thermodynamically possible below 289.8 K and entire pressure range considered. Our results highlight, for the first time, that the endohedral cavity of C60SW66 is a promising new medium for hydrogen storage due to its binding energies (−0.26 eV) and its hydrogen storage weight percentage (5.3%) that are close to the optimal conditions specified by DOE for commercial use. In addition, this study opens up a new discovery of Stone-Wales defective C60 fullerene for further endohedral cavity applications.

Computational assessment of the use of graphene-based nanosheets as PtII chemotherapeutics delivery systems.

Graphene is the newest form of elemental carbon and it is becoming rapidly a potential candidate in the framework of nano-bio research. Many reports confirm the successful use of graphene-based materials as carriers of anticancer drugs having relatively high loading capacities compared with other nanocarriers. Here, the outcomes of a systematic study of the adsorption behavior of FDA approved PtII drugs cisplatin, oxaliplatin, and carboplatin on surface models of pristine, holey, and nitrogen-doped holey graphene are reported. DFT investigations in water solvent have been carried out considering several initial orientations of the drugs with respect to the surfaces. Adsorption free energies, calculated including basis set superposition error (BSSE) corrections, result to be significantly negative for many of the drug@carrier adducts indicating that tested layers could be used as potential carriers for the delivery of anticancer PtII drugs. The reduced density gradient (RDG) analysis allows to show that many kinds of non-covalent interactions, including canonical H-bond, are responsible for the stabilization of the formed adducts.

Master equation modeling of blackbody infrared radiative dissociation (BIRD) of hydrated peroxycarbonate radical anions.

Molecular cluster ions, which are stored in an electromagnetic trap under ultra-high vacuum conditions, undergo blackbody infrared radiative dissociation (BIRD). This process can be simulated with master equation modeling (MEM), predicting temperature-dependent dissociation rate constants, which are very sensitive to the dissociation energy. We have recently introduced a multiple-well approach for master equation modeling, where several low-lying isomers are taken into account. Here, we experimentally measure the BIRD of CO4●-(H2O)1,2 and model the results with a slightly modified multiple-well MEM. In the experiment, we exclusively observe loss of water from CO4●-(H2O), while the BIRD of CO4●-(H2O)2 leads predominantly to loss of carbon dioxide, with water loss occurring to a lesser extent. The MEM of two competing reactions requires empirical scaling factors for infrared intensities and the sum of states of the loose transition states employed in the calculation of unimolecular rate constants so that the simulated branching ratio matches the experiment. The experimentally derived binding energies are ΔH0(CO4●--H2O) = 45 ± 3kJ/mol, ΔH0(CO4●-(H2O)-H2O) = 41 ± 3kJ/mol, and ΔH0(CO2-O2●-(H2O)2) = 37 ± 3kJ/mol. Quantum chemical calculations on the CCSD(T)/aug-cc-pVTZ//CCSD/aug-cc-pVDZ level, corrected for the basis set superposition error, yield binding energies that are 2-5kJ/mol higher than experiment, within error limits of both experiment and theory. The relative activation energies for the two competing loss channels are as well fully consistent with theory.

A Computational Characterization of CH4@C60

The recently synthetically prepared endohedral CH4@C60 was characterized here using calculations—namely its structure, energetics, thermodynamics, and vibrational spectrum. The calculations were carried out with DFT (density-functional theory) methods, namely by the DFT M06-2X functional and MP2, as well as B2PLYPD advanced correlated, treatments with the standard 6-31++G** and 6-311++G** basis sets, corrected for the basis set superposition error evaluated using the approximative Boys–Bernardi counterpoise method. The symmetry of the endohedral obtained in the geometry optimizations was tetrahedral T. The energetics of CH4 encapsulation into C60 was attractive (i.e., with a negative encapsulation-energy term), producing a substantial energy gain of −13.94 kcal/mol at the most advanced computational level, B2PLYPD/6-311++G**. The encapsulation equilibrium constants for CH4@C60 were somewhat higher than previously found with the CO@C60 system. For example at 500 K, the encapsulation equilibrium constant for CH4@C60 had a value one order of magnitude larger than for CO@C60. The encapsulation thermodynamic characteristics suggest that high-pressure and high-temperature synthesis could in principle also be possible for CH4@C60.

Size Matters: Computational Insights into the Crowning of Noble Gas Trioxides.

In pursuit of enhancing the stability of the highly explosive and shock-sensitive compound XeO3, we performed quantum chemical calculations to investigate its possible complexation with electron-rich crown ethers, including 9-crown-3, 12-crown-4, 15-crown-5, 18-crown-6, and 21-crown-7, as well as their thio analogues. Furthermore, we expanded our study to other noble gas trioxides (NgO3), namely, KrO3 and ArO3. The basis set superposition error (BSSE) corrected interaction energies for these adducts range from -13.0 kcal/mol to -48.2 kcal/mol, which is notably high for σ-hole-mediated noncovalent interactions. The formation of these adducts was observed to be more favorable with the increase in the ring size of the crowns and less favorable while going from XeO3 to ArO3. A comprehensive analysis by various computational tools such as the mapping of the electrostatic potential (ESP), Wiberg bond indices (WBIs), Bader's theory of atoms-in-molecules (AIM), natural bond orbital (NBO) analysis, noncovalent interaction (NCI) plots, and energy decomposition analysis (EDA) revealed that the C-H···O interactions, as well as dispersion interactions, play a pivotal role in stabilizing adducts involving larger crowns. A noteworthy outcome of our study is the revelation of a coordination number of 9 for xenon in the complex formed between XeO3 and the thio analogue of 18-crown-6, which is higher than the largest number reported to date.

Capturing CO2 in Quadrupolar Binding Pockets: Broadband Microwave Spectroscopy of Pyrimidine-(CO2)n, n = 1,2.

Pyrimidine has two in-plane CH(δ+)/N̈(δ-)/CH(δ+) binding sites that are complementary to the (δ-/2δ+/δ-) quadrupole moment of CO2. We recorded broadband microwave spectra over the 7.5-17.5 GHz range for pyrimidine-(CO2)n with n = 1 and 2 formed in a supersonic expansion. Based on fits of the rotational transitions, including nuclear hyperfine splitting due to the two 14N nuclei, we have assigned 313 hyperfine components across 105 rotational transitions for the n = 1 complex and 208 hyperfine components across 105 rotational transitions for the n = 2 complex. The pyrimidine-CO2 complex is planar, with CO2 occupying one of the quadrupolar binding sites, forming a structure in which the CO2 is stabilized in the plane by interactions with the C-H hydrogens adjacent to the nitrogen atom. This structure is closely analogous to that of the pyridine-CO2 complex studied previously by (Doran, J. L. J. Mol. Struct. 2012, 1019, 191-195). The fit to the n = 2 cluster gives rotational constants consistent with a planar cluster of C2v symmetry in which the second CO2 molecule binds in the second quadrupolar binding pocket on the opposite side of the ring. The calculated total binding energy in pyrimidine-CO2 is -13.7 kJ mol-1, including corrections for basis set superposition error and zero-point energy, at the CCSD(T)/ 6-311++G(3df,2p) level, while that in pyrimidine-(CO2)2 is almost exactly double that size, indicating little interaction between the two CO2 molecules in the two binding sites. The enthalpy, entropy, and free energy of binding are also calculated at 300 K within the harmonic oscillator/rigid-rotor model. This model is shown to lack quantitative accuracy when it is applied to the formation of weakly bound complexes.

Theoretical study on formation mechanism of acetic acid associating configurations and their distributions under saturated conditions.

The vapor-liquid equilibrium (VLE) properties of acetic acid systems generally behave strong non-ideality due to the associating interaction among acetic acid molecules. Theoretical study of the associating mechanism will provide guidance for the VLE property prediction, which is crucial for the designing on the separation process of the acetic acid systems. In this work, the association conformers and their distribution on acetic acid molecules in saturated gas and liquid phase were firstly studied. The proportions of the acetic acid monomer and multimers were obtained, which will contribute to the foundation for the vapor-liquid equilibrium simulations. The association mechanism on acetic acid molecules was then investigated by comparing among the structures and non-bonded interaction energies of different dimers. The structure of the cyclic dimer containing two OC-HO hydrogen bonds, may be found probably when acetic acid molecules approached. Electronic properties of different acetic acid dimers showed that the electrons around carbonyl oxygen atoms were deflected by the attraction of hydrogen atoms in the other molecule, which polarized the acetic acid molecules when the hydrogen bonds between acetic acid molecules were formed, providing theoretical basis for the polarized acetic acid molecular model. In this work, the molecular dynamics (MD) simulations and DFT calculations were conducted through the software GROMACS and Gaussian 09, respectively. For the MD simulations, the OPLS-AA force field was used as the atomic force field, with the cubic simulation cells constructed by Packmol program. For the DFT calculations, the M06-2X functional was employed for the optimization of the associating structures with the 6-311G** basis sets. Hydrogen bonding energies of dimers were corrected for the basis set superposition error (BSSE) and the deformation energies of monomers. Furthermore, the energy decomposition analysis was conducted at DFT/M06-2X/def-tzp level by the ADF software, and the wave function analysis was conducted by the Multiwfn software including the atom in molecule (AIM) topology analysis, the electronic potential analysis, and the electron density difference analysis.

Tetraoxa[8]circulene monolayer as hydrogen storage material: model with Boys–Bernardi corrections within density functional theory

The parameters of molecular hydrogen adsorption on a tetraoxa[8]circulene monolayer were studied using the density functional theory with dispersion interaction corrections (semi-empirical and analytical). The calculations were carried out using two different approaches to the system wave function representation: atomic-like orbital basis set and plane wave basis. Utilizing a less computationally expensive pseudoatomic basis, it is possible to obtain results for molecular hydrogen adsorption consistent with values calculated with plane waves if the atomic-like basis is optimized and basis set superposition error is corrected for both hydrogen binding energy and geometrical characteristics. Otherwise, the H2 binding energy will be overestimated by 4–6 times (sometimes even more, by 20); and the hydrogen-monolayer distance will be underestimated by 10-20%. The obtained optimized parameters of the pseudoatomic basis set can be used for further study of the modified forms of the tetraoxa[8]circulene monolayer. Moreover, our calculations showed that the hydrogen binding to a pristine tetraoxa[8]circulene monolayer is predominantly van der Waals with an energy of 60–90 meV, which is several times less than the desired range of 200–600 meV. To achieve such values, it will be necessary to modify the surface of the monolayer, creating more active sorption cites, for example, by decorating it with metals or applying structural defects.

Investigation on bare ZnO nanotubes and nanosheet as electrode materials for potassium-ion batteries: A DFT search

Within this work, the possibility of using (5,0), (6,0), (7,0), (8,0), and (9,0) zigzag ZnO nano-tubes and a ZnO nano-sheet (ZnONS) was investigated in potassium-ion batteries (KIBs) through the B3LYP-gCP-D3/6-31G* scheme. The cell voltage, ion diffusion coefficient, the maximum energy barrier for the migration of K+ and the adhesion energies of K+ and K of (5,0) nano-tube were 0.93 V, 5.31 × 10−8 cm2/s, –33.4 kcal/mol, respectively. The results showed that the impact of the dispersion term (D3) on the K and K+ adhesion energies was more than that of the gCP (basis set superposition error). A reduction in the curvature of the ZnONS dramatically weakened the interaction of the K atom, whereas it had a slight impact on the interaction of K+. Therefore, a decrease in the curvature of the ZnONS increased the cell voltage to 1.21 V. We can use ZnO nano-structures as a promising anode for KIBs.