Density Functional Theory Level Research Articles

Deposition products predicted from conceptual DFT: The hydrolysis reactions of MoF6, WF6, and UF6.

Metal hexafluorides hydrolyze at ambient temperature to deposit compounds having fluorine-to-oxygen ratios that depend upon the identity of the metal. Uranium-hexafluoride hydrolysis, for example, deposits uranyl fluoride (UO2F2), whereas molybdenum hexafluoride (MoF6) and tungsten hexafluoride deposit trioxides. Here, we pursue general strategies enabling the prediction of depositing compounds resulting from multi-step gas-phase reactions. To compare among the three metal-hexafluoride hydrolyses, we first investigate the mechanism of MoF6 hydrolysis using hybrid density functional theory (DFT). Intermediates are then validated by performing anharmonic vibrational simulations and comparing with infrared spectra [McNamara et al., Phys. Chem. Chem. Phys. 25, 2990 (2023)]. Conceptual DFT, which is leveraged here to quantitatively evaluate site-specific electrophilicity and nucleophilicity metrics, is found to reliably predict qualitative deposition propensities for each intermediate. In addition to the nucleophilic potential of the oxygen ligands, several other contributing characteristics are discussed, including amphoterism, polyvalency, fluxionality, steric hindrance, dipolar strength, and solubility. To investigate the structure and composition of pre-nucleation clusters, an automated workflow is presented for the simulation of particle growth. The workflow entails a conformer search at the density functional tight-binding level, structural refinement at the hybrid DFT level, and computation of a composite free-energy profile. Such profiles can be used to estimate particle nucleation kinetics. Droplet formation is also considered, which helps to rationalize the different UO2F2 particle morphologies observed under varying levels of humidity. Development of predictive methods for simulating physical and chemical deposition processes is important for the advancement of material manufacturing involving coatings and thin films.

Unraveling pnicogen bonding cooperativity: Insights from molecular electrostatic potential analysis.

A theoretical investigation on the cooperativity of a series of binary, ternary, and quaternary complexes interconnected by pnicogen bonds has been conducted using calculations at the M06-2X/aug-cc-pVTZ level of density functional theory. By measuring changes in the molecular electrostatic potential (MESP) at the nucleus of interacting atoms in all of the complexes, it is possible to quantify the substantial reorganization of the electron density triggered by the formation of pnicogen bonds. The positive change in MESP, indicating a loss of electron density from the donor molecule in a dimer, facilitates the acceptance of electron density from a third molecule, resulting in the formation of a ternary complex with a stronger pnicogen bond compared to the one present in the binary complex. Similarly, the acceptor molecule in a dimer with a negative change in MESP showed an enhanced tendency to donate electron density to an electron-deficient third molecule. The MESP analysis provided valuable insights into the donor/acceptor characteristics of pnicogen bonds within the quaternary complexes. The proposed MESP hypotheses are consistent with the positive cooperativity observed in the pnicogen-bonded clusters. To quantify the changes in MESP, both at the donor atom (ΔVdonor ) and the acceptor atom (ΔVacceptor ), for all pnicogen bonds in the cluster, the total change in MESP (ΔΔVn ) was measured as ΔΔVn = ∑(ΔVdonor )-∑(ΔVacceptor ). Remarkably, ΔΔVn exhibited a strong linear relationship with the sum of the bond energies of the pnicogen bonds in the cluster. This establishes the MESP analysis as a robust approach for understanding the strength and cooperative behavior of pnicogen-bonded clusters. Additionally, the MESP features provided clear evidence of pnicogen bond formation, further supporting the reliability of this approach.

Unraveling the delayed fluorescence mechanism of copper(I) halide-phosphine emitters from DFT calculations

Several copper complexes exhibiting luminescent properties have been studied. In this context, the possibility of incorporating them into the architecture of organic light-emitting diode (OLED) devices has been investigated to improve their efficiency and photophysical stability for predicting the suitability and character of the emissive material. Specifically, we unraveled the excitation mechanism of the Cu(I)X(dppt)(PPh3) complex [X = Br, I, dppt = 3,4-bis(diphenylphosphino)thiophene]. Since the intersystem crossing (ISC) depicts a necessary process, where the knowledge of the rate constant value enables the assessment of the suitability of the material, we calculated the reverse and intersystem crossing rates for the Cu(I) complexes contrasting with pure organic thermally activated delayed fluorescence (TADF) emitters, with the goal to emphasize that the structural design of the mononuclear copper(I) complexes results in similar singlet–triplet gaps, ΔEST, values (∼0.1 eV). Moreover, it shows a remarkable enhancement of spin–orbit coupling, which allows achieving ISC rates in the ns scale. The calculations were made in the Time-Dependent Density Functional Theory (TD-DFT) level framework with the accurate response of large molecules studied here.

Discovery of a series of silicon-based ferrimagnets in CrMnSin (n = 4-20) clusters.

Herein, the structural evolution, electronic and magnetic properties of silicon clusters with two different dopants, CrMnSin (n = 4-20) clusters were investigated at density functional theory (DFT) level. Small-sized CrMnSin (n = 4-9) clusters tend to adopt bipyramid-based geometries, while clusters with sizes n = 10 and 11 prefer to opening cage-like structures. For sizes n = 12 to 14, the half-encapsulated structures gradually transform into closed-cage Cr@Sin structures, with the Mn atom exposed outside. Starting from size 15, both the Cr and Mn atoms are completely encapsulated by silicon atoms. Meanwhile, the Cr and Mn atoms in smaller-sized CrMnSin (n = 4-7) clusters tend to be separated, while they prefer to stay together for larger sizes. Cr atom always acts as electron donor, but not for Mn atom. From the average binding energies, one can conclude that it is easier to form larger size clusters. Smaller and larger sized CrMnSin (n = 4-9 and 19-20) clusters prefer to exhibit ferromagnetic Cr-Mn coupling, while sizes n = 10-18 always exhibit ferrimagnetic state. To our knowledge, the CrMnSin clusters is the first kind of neutral transition-metal doped semiconductor clusters that show ferrimagnetic state within a wide size range.

PREPARATION, CHARACTERISATION, EVALUATION AND DFT ANALYSIS OF CILNIDIPINE-L-PHENYLALANINE COCRYSTAL

Objective: The objective of this study was to prepare, characterise and evaluate pharmaceutical cocrystals of Cilnidipine using L-phenylalanine as the coformer to enhance the aqueous solubility of Cilnidipine. It was also proposed to study the mechanism of cocrystal formation based on Density Functional Theory (DFT) using Gaussian software. Methods: To overcome the limitation of poor aqueous solubility of Cilnidipine, a 1:1 pharmaceutical cocrystal of Cilnidipine was prepared using L-phenylalanine as the coformer by liquid assisted grinding (LAG) technique. The resultant cocrystals were characterised by Fourier transform-infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and field emission scanning electron microscopy (FE-SEM). They were evaluated for their saturation solubility in water. The mechanism of cocrystal formation was studied at the DFT level of theory. Results: The band broadening of the–NH and–NO peaks in FTIR spectra of Cilnidipine indicated the formation of hydrogen bonds in the prepared cocrystals. A single sharp melting endotherm at 218.40 °C in the DSC curve confirmed the formation of cocrystals. The appearance of new peaks in the PXRD pattern of the prepared cocrystals showed the formation of a new crystalline phase. FE-SEM analysis also confirmed the above findings. The prepared cocrystals exhibited 3.31 folds enhancement in saturation solubility. The DFT analysis showed the formation of intrmolecular hydrogen bonding between the–NO of Cilnidipine and–NH of L-phenylalanine. Conclusion: The present study demonstrated a successful approach for enhancing the solubility of poorly water-soluble drug Cilnidipine by cocrystallisation technique using L-phenylalanine as the coformer.

Simple scaling of the empirical London dispersion corrections in DFT geometry optimizations of prototypical nonlinear optical crystals

AbstractThe quantum treatment of electrons at the Kohn‐Sham Density Functional Theory (DFT) level of approximation is used in order to optimize the structure of four organic and organo‐metallic crystalline systems, starting from experimentally determined structures, allowing subsequent quantum‐level theoretical analysis, the accent here being put on crystals having nonlinear optical (NLO) properties. By employing DFT, one must select an exchange‐correlation functional (XCF), that is, a mathematical description of the electron interactions. Among most of the XCFs, a well‐known general discrepancy is the lack of London‐type interactions description. One of the most popular correction schemes consists of adding a posteriori the contribution of these interactions by using empirical expressions. Here, the approach relies on the simple D* scheme, a variation of the D2 correction originally elaborated by Grimme for molecular clusters, where the D2 correction is scaled to account for the interactions in the crystal solid state. The performance of this simple D* scheme is demonstrated and the most suitable scaling factors for four prototypical organic and organo‐metallic NLO crystals are determined for four representative XCFs: zero (no correction) for PBESol, PBESol0, and B97X, and 0.7 for B3LYP.

Possible Roles of Transition Metal Cations in the Formation of Interstellar Benzene via Catalytic Acetylene Cyclotrimerization.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous interstellar molecules. However, the formation mechanisms of PAHs and even the simplest cyclic aromatic hydrocarbon, benzene, are not yet fully understood. Recently, we reported the statistical and dynamical properties in the reaction mechanism of Fe+-catalyzed acetylene cyclotrimerization, whereby three acetylene molecules are directly converted to benzene. In this study, we extended our previous work and explored the possible role of the complex of other 3d transition metal cations, TM+ (TM = Sc, Ti, Mn, Co, and Ni), as a catalyst in acetylene cyclotrimerization. Potential energy profiles for bare TM+-catalyst (TM = Sc and Ti), for TM+NC--catalyst (TM = Sc, Ti, Mn, Co, and Ni), and for TM+-(H2O)8-catalyst (TM = Sc and Ti) systems were obtained using quantum chemistry calculations, including the density functional theory levels. The calculation results show that the scandium and titanium cations act as efficient catalysts in acetylene cyclotrimerization and that reactants, which contain an isolated acetylene and (C2H2)2 bound to a bare (ligated) TM cation (TM = Sc and Ti), can be converted into a benzene-metal-cation product complex without an entrance barrier. We found that the number of electrons in the 3d orbitals of the transition metal cation significantly contributes to the catalytic efficiency in the acetylene cyclotrimerization process. On-the-fly Born-Oppenheimer molecular dynamics (BOMD) simulations of the Ti+-NC- and Ti+-(H2O)8 complexes were also performed to comprehensively understand the nuclear dynamics of the reactions. The computational results suggest that interstellar benzene can be produced via acetylene cyclotrimerization reactions catalyzed by transition metal cation complexes.

Atomically dispersed zeolite-supported rhodium complex: Selective and stable catalyst for acetylene semi-hydrogenation

Supported rhodium catalysts are known to be unselective for semi-hydrogenation reactions. Here, by tuning the electronic structure of supported mononuclear rhodium sites determined by the metal nuclearity and the electron-donor properties of the support, we report that atomically dispersed HY zeolite-supported rhodium with reactive acetylene ligands affords a stable ethylene selectivity > 90 % for acetylene semi-hydrogenation at 373 K and atmospheric pressure, even when ethylene is present in a large excess over acetylene. Infrared and X-ray absorption spectra and measurements of rates of the catalytic reaction complemented with calculations at the level of density functional theory show how the catalyst performance depends on the electronic structure of the rhodium, influenced by the support as a ligand that is a weak electron donor.

Periodic table representation of binary, ternary and higher-order systems of inorganic compounds

We enumerate the chemical elements by using the periodicity of the Mendeleev Periodic Table, where the rows reflect the principal quantum number of the electronic configuration of the elements as isolated atoms. By doing that we assign the Periodic Number (PN) to the elements, which expresses much more clearly the chemical similarity between them along the groups. Moving from the unary to higher-order systems, the PN representation shows in an elegantly simple and holistic manner the periodicity of chemical properties and phase stability.By using the PNs of the constituent elements of binary systems, we construct the phase map in which we identify seven regions where phases are not formed, namely the non-former regions. Except for very few distinct systems that violate the identified non-former regions, the seven forbidden regions represent the phase space where phases are not formed in any composition of the constituent elements, whose PNs fall in the given PN ranges also for higher-order systems. In fact, the PN representation of the binary phases map can be easily extended to any higher-order chemical systems to delimit the regions where to search for possible phases, namely the former regions.The powerful usage of the PN representation is seen in the chemical property trends we report for the equiatomic binary phases, for which we calculate, after fully relaxing the crystal structures, the enthalpy of formation, the cohesive energy, the lattice stability and the bulk modulus by using total energy calculations at Density Functional Theory level.

Phenylpropiolic acid isolated in cryogenic nitrogen and xenon matrices: NIR and UV-induced study.

Phenylpropiolic acid (C6H5C≡CCOOH, PPA) isolated in nitrogen and xenon cryogenic matrices was studied by infrared spectroscopy. The experimental studies were complemented by a series of quantum chemical calculations carried out at the density functional theory (B3LYP) and MP2 levels of theory (with different basis sets). The calculations predicted the existence of two planar PPA conformers, differing in the arrangement of the carboxylic group. The higher-energy trans-PPA conformer has a negligible population in the gas phase at room temperature and was prepared in situ in the N2 cryomatrix through vibrationally-induced rotamerization of the lower-energy cis-PPA conformer, achieved using selective narrowband infrared excitation of the OH stretching coordinate of the latter species. Broadband UV (λ > 235nm) irradiation of matrix-isolated cis-PPA was also undertaken, leading to the observation of cis-PPA → trans-PPA isomerization. No other UV-induced photoreactions were observed. The in situ generated trans-PPA conformer was found to decay back to cis-PPA in the dark by tunneling, and its lifetimes under different experimental conditions were determined. The assignment of the infrared spectra of both conformers is presented, considerably extending the vibrational information available on this molecule.

An insight into the thermal decomposition mechanism of 1-Butyl-3-methyl-imidazolium-5-aminotetrazolate guided by Py-GC–MS and DFT

Ionic liquids containing azole-based heterocyclic rings are potentially energetic due to the high nitrogen content and positive heat of formation. The thermal decomposition mechanism of 1-Butyl-3-methyl-imidazolium-5-aminotetrazolate (BMIMAT) has been studied by use of Py-GC–MS and B3LYP/6–311 + G(d,p) level of density functional theory (DFT). The mechanism of decomposition observed is a bimolecular nucleophilic substitution (SN2) reaction. The kinetics of decomposition is studied using Kissinger and Ozawa-Flynn-Wall (FWO) methods and the activation energy (Ea) obtained is complemented with computational studies.

Cryo-IR spectroscopy and cryo-kinetics of cluster N2 adsorbate complexes of tantalum cluster cations Ta5-8.

We present an IR-PD study of tantalum cluster adsorbate complexes [Tan(N2)m]+, abbreviated (n,m), n = 5-8. We utilize infrared spectroscopy of isolated and size selected clusters as prepared and characterized by a cryogenic tandem ion trap setup, and we augment our experiments with quantum chemical simulations at the level of density functional theory. The cluster adsorbate complexes (n,m) reveal vibrational bands above 2000cm-1, which indicate end-on coordinated μ1-N2 oscillators, and bands below 2000cm-1, which indicate side-on μ2-κN:κN,N coordinated ones. We observe a general increase in spectral complexity and an inhomogeneous broadening, mainly towards the red, at certain points of N2 loading m, which originates from an increasingly higher amount of double and triple N2 coordination at Ta sites, eventually at all of them. Other than the small tantalum clusters Tan+, n = 2-4, the IR-PD spectra of the initial N2 adsorbate species (n,1), n = 5-8, provide strong evidence for a lack of spontaneous N2 cleavage. Spontaneous N2 cleavage by Tan+, n = 5-8, seems suppressed. Therefore, the ability of a small Ta cluster to cleave dinitrogen disappears with one more tantalum core atom. The study of stepwise N2 adsorption on size selected Tan+, n = 5-8 clusters revealed adsorption limits m(max) of [Tan(N2)m]+ that are independent of cluster size within this size range. Cryo-adsorption kinetics at 26K allowed for kinetic fits to consecutive N2 adsorption steps, and the fits revealed significant N2 desorption rates upon higher N2 loads, and the cluster adsorbate complexes eventually reached equilibrium. Some enhanced N2 desorption rates point towards likely adsorbate shell reorganization, and there is also some evidence for the coexistence of isomeric cluster adsorbate complexes.

Excitonic effects on the optical spectra of TiB2 nanosheets

Two-dimensional (2D) transition metal borides, have recently attracted tremendous interest and become an emerging class of 2D materials due to their intriguing properties. We report systematic investigation of stability, electronic properties and optical activity of 2D-TiB2 nanosheets using first-principles calculations. By combining elastic and phonon-dispersion calculations, we substantiated the mechanical and dynamic stability of 2D-TiB2 nanosheets. Our results of elastic calculations reveal that addition of an extra layer destroys the auxetic behaviour of monolayer (ML) 2D-TiB2 with significant reduction in the brittleness. Further, based on the spin-polarised electronic structure calculations, we find that a low-dimensional metallic state of ML can be achieved by tuning the distance between the titanium and boron layers. The calculations clearly reveal that metallic nature does not destroys the auxetic behaviour of ML. Subsequently, we investigated the optical response of 2D-TiB2 nanosheets (ML and bilayer (BL)) at the level of density functional theory and many-body perturbation theory. The results obtained by solving Bethe–Salpeter equation (GW+BSE formalism) shows that excitonic effects causes a slight blue-shift in the absorption spectra of the nanosheets with ML being optically active with sharp peaks in infrared (IR) and ultraviolet (UV) regions while BL shows the reduced optical activity across wide range of photon energies spanning the near-IR to UV region. In addition, electronic polarisability of the nanosheet decreases with addition of another layer in ML 2D-TiB2. Further investigation of transition probabilities clearly indicates that the response of ML at Dirac point is tunable by spin–orbital coupling effects which makes these nanosheets promising for spintronic applications. The BL exhibits distinct electronic, and optical properties compared to ML. Our study unravels the structural, elastic, electronic, and optical properties of 2D-TiB2 nanosheets and suggests them as promising candidate for variety of optoelectronic and spintronic applications.

Nanosecond MD of battery cathode materials with electron density description

Potentials derived with machine learning algorithms achieve the accuracy of high-fidelity quantum mechanical computations such as density functional theory (DFT), while allowing orders of magnitude lower computational time. In this work, we demonstrate the use of uncertainty aware equivariant graph neural networks for predicting spin-resolved electron densities, forces, and energies of the Na3V2(PO4)3 NASICON structured cathode. Due to the speedup in computational time, we are able to investigate structures of ∼300 atoms for 200 million timesteps. The ability to model larger systems on the nanosecond length scale with maintaining DFT level accuracy allowed critical insights into the diffusion characteristics of Na-ions, associated electron transfer processes, and dependence of diffusivity on sodium concentration in the structure.

Comparison of reactive sites of different conjugated linoleic acid molecules by quantum chemical calculations

AbstractIn this paper, quantum chemical calculations and Gaussian 09 software were used to investigate the similarities and differences in the reactive sites of different fatty acids. The molecule structures of linoleic acid (LA) and four conjugated linoleic acid (CLA) were analyzed at the level of density functional theory. Molecular geometries and energies, frontline molecular orbitals, and surface electrostatic potentials were also analyzed. The results showed that the reactive of LA and CLA among the five fatty acids were all near the –C = C– structure and the carboxyl hydrogen atom, 9c, 11t CLA and 10t, 12c CLA were more reactive compared with 9t, 11t CLA, 10t, 12t CLA. This study can provide a theoretical basis for revealing the relationship between different structures and properties of fatty acids and also provide a guidance for the selection of fatty acids in the oil and fat industry.Practical Applications: This experiment compares the differences between the reactive sites of CLA and the four CLAs at the molecular structure level, which can be used to deepen the understanding of the structure‐property relationship of different fatty acids and also provides a theoretical basis for the selection of fatty acids in the food and oil industry.

Ultrahigh power factor of Bi/Zn co-doped SnSe: Mechanical and thermoelectric properties on DFT level

Tin selenide-based materials have attracted much attention recently because of their unique properties. This study employs first-principles calculations and density functional theory (DFT) to investigate the impact of Bismuth and Zinc co-doping on the electronic, mechanical, and thermoelectric properties of SnSe. The co-doped system exhibits a triclinic crystal structure and shows enhanced electrical conductivity and the generation of n-type carriers. The co-doped SnSe also demonstrates improved mechanical stability, higher susceptibility to shear deformation, and increased deformability under shear stresses. Thermoelectric calculations reveal significantly enhanced power factor (PF) values compared to pristine SnSe and single-doped Zn and Bi SnSe structures, with a maximum PF of 63.0 μV/Kcm at 800 K. These findings highlight the potential of Bi and Zn co-doped SnSe as a promising high-performance thermoelectric material and provide valuable insights for further research in SnSe-based materials.

Unraveling pyrolysis mechanisms of lignin dimer model compounds: Neural network-based molecular dynamics simulation investigations

Unraveling the pyrolysis mechanisms of lignin is of great importance for effective lignin utilization. However, both conventional quantum mechanical method and molecular dynamics (MD) simulations based on empirical potentials, e.g., the ReaxFF, cannot guarantee simultaneous accuracy and efficiency in exploring lignin pyrolysis mechanisms. Here, we developed a neural network (NN) force field for four types of representative lignin dimers based on 56,164 structures at the level of density functional theory (DFT). Such NN model was demonstrated to possess more accurate predictive power in both energetic and atomistic force properties than ReaxFF and was far more efficient than QM method. The MD simulations with the NN model showed that entire pyrolysis process can be divided into three stages dependent on the reaction temperature: homolytic cleavage of C–C bond and C-O bond, the changes from methoxy group to hydroxy, methyl, and formyl group, ring-opening reactions and the ring structure evolutions, and some novel reactions. The NN-based MD has provided us an atomic-level understanding of lignin pyrolysis and enabled us to build a comprehensive lignin pyrolysis network by means of the reactions disclosed based on the NN-based MD, which provided a useful guide for taking advantage of lignin more effectively.

Exploring the Mechanism of the Intramolecular Diels-Alder Reaction of (2E,4Z,6Z)-2(allyloxy)cycloocta-2,4,6-trien-1-one Using Bonding Evolution Theory.

In the present work, the bond breaking/forming events along the intramolecular Diels-Alder (IMDA) reaction of (2E,4Z,6Z)-2(allyloxy)cycloocta-2,4,6-trien-1-one have been revealed within bonding evolution theory (BET) at the density functional theory level, using the M05-2X functional with the cc-pVTZ basis set. Prior to achieving this task, the energy profiles and stationary points at the potential energy surface (PES) have been characterized. The analysis of the results finds that this rearrangement can proceed along three alternative reaction pathways (a-c). Paths a and b involve two steps, while path c is a one-step process. The first step in path b is kinetically favored, and leads to the formation of an intermediate step, Int-b. Further evolution from Int-b leads mainly to 3-b1. However, 2 is the thermodynamically preferred product and is obtained at high temperatures, in agreement with the experimental observations. Regarding the BET analysis along path b, the breaking/forming process is described by four structural stability domains (SSDs) during the first step, which can be summarized as follows: (1) the breaking of the C-O bond with the transfer of its population to the lone pair (V(O)), (2) the reorganization of the electron density with the creation of two V(C) basins, and (3) the formation of a new C-C single bond via the merger of the two previous V(C) basins. Finally, the conversion of Int-b (via TS2-b1) occurs via the reorganization of the electron density during the first stage (the creation of different pseudoradical centers on the carbon atoms as a result of the depopulation of the C-C double bond involved in the formation of new single bonds), while the last stage corresponds to the non-concerted formation of the two new C-C bonds via the disappearance of the population of the four pseudoradical centers formed in the previous stage. On the other hand, along path a, the first step displays three SSDs, associated with the depopulation of the V(C2,C3) and V(C6,C7) basins, the appearance of the new monosynaptic basins V(C2) and V(C7), and finally the merging of these new monosynaptic basins through the creation of the C2-C7 single bond. The second step is described by a series of five SSDs, that account for the reorganization of the electron density within Int-a via the creation of four pseudoradical centers on the C12, C13, C3 and C6 carbon atoms. The last two SSDs deal with the formation of two C-C bonds via the merging of the monosynaptic basins formed in the previous domains.

Photovoltaic response promoted via intramolecular charge transfer in pyrazoline-based small molecular acceptors: Efficient organic solar cells

Herein, a series of pyrazoline based non-fullerene compounds (THP1-THP8) having ladder-like backbone was designed by structural modulation with various electron accepting moieties. The density functional theory (DFT) and time-dependent functional theory (TD-DFT) study was executed at M06/6-311G(d,p) level for structural optimization and to determine the electronic and optical characteristics of the pyrazoline based chromophores. The optimized structures were employed to execute frontier molecular orbital (FMO), transition density matrix (TDM), density of state (DOS), open circuit voltage (Voc) and reorganization energy analyses at the aforementioned level of DFT to comprehend the photovoltaic (PV) response of THP1-THP8. The red-shifted absorption spectrum (512.861–584.555 nm) with reduced band gap (2.507–2.881 eV) allow considerable charge transferal from HOMO to LUMO in all the studied compounds. Global reactivity parameters (GRPs) demonstrated high softness with considerable reactivity in THP1-THP8. Moreover, remarkable Voc values (2.083–2.973 V) were noted for all the derivatives (THP1-THP8). However, THP2 with lowest energy gap (2.364 eV), highest λmax (617.482 nm) and softness (0.423 eV) values is considered good candidate among afore-said chromophores. Hence, the studied chromophores with efficient properties are appropriate for experimentalists in terms of manufacturing of efficient OSCs.

Review of Applications of Density Functional Theory (DFT) Quantum Mechanical Calculations to Study the High-Pressure Polymorphs of Organic Crystalline Materials.

Since its inception, chemistry has been predominated by the use of temperature to generate or change materials, but applications of pressure of more than a few tens of atmospheres for such purposes have been rarely observed. However, pressure is a very effective thermodynamic variable that is increasingly used to generate new materials or alter the properties of existing ones. As computational approaches designed to simulate the solid state are normally tuned using structural data at ambient pressure, applying them to high-pressure issues is a highly challenging test of their validity from a computational standpoint. However, the use of quantum chemical calculations, typically at the level of density functional theory (DFT), has repeatedly been shown to be a great tool that can be used to both predict properties that can be later confirmed by experimenters and to explain, at the molecular level, the observations of high-pressure experiments. This article's main goal is to compile, analyze, and synthesize the findings of works addressing the use of DFT in the context of molecular crystals subjected to high-pressure conditions in order to give a general overview of the possibilities offered by these state-of-the-art calculations.