Calculated Energy Differences Research Articles

Palladium-Catalyzed Enantioselective 7-exo-Trig Carbopalladation/Carbonylation: Cascade Reactions To Achieve Atropisomeric Dibenzo[b,d]azepin-6-ones.

Enantioselective 7-exo-trig cyclocarbopalladation-initiated carbonylation cascade reactions, leading to seven-membered dibenzo[b,d]azepin-6-ones containing a thermodynamically controlled stereogenic axis, have been realized for the first time. A series of 7-acetate- or 7-acetamide-substituted dibenzo[b,d]azepin-6-ones are obtained under atmospheric pressure of CO in good yields with excellent diastereo- and enantioselectivities. The calculated energy difference between the diastereoisomers generated from the stereogenic biaryl axis and the stereogenic center is approximately 2.8 kcal/mol, which agrees with the excellent diastereoselectivity observed.

Accelerate stochastic calculation of random-phase approximation correlation energy difference with an atom-based correlated sampling

A kernel polynomial method is developed to calculate the random phase approximation (RPA) correlation energy. In the method, the RPA correlation energy is formulated in terms of the matrix that is the product of the Coulomb potential and the density linear response functions. The integration over the matrix’s eigenvalues is calculated by expanding the density of states of the matrix in terms of the Chebyshev polynomials. The coefficients in the expansion are obtained through stochastic sampling. Since it is often the energy difference between two systems that is of much interest in practice, another focus of this work is to develop a correlated sampling scheme to accelerate the convergence of the stochastic calculations of the RPA correlation energy difference between two similar systems. The scheme is termed the atom-based correlated sampling (ACS). The performance of ACS is examined by calculating the isomerization energy of acetone to 2-propenol and the energy of the water–gas shift reaction. Using ACS, the convergences of these two examples are accelerated by 3.6 and 4.5 times, respectively. The methods developed in this work are expected to be useful for calculating RPA-level reaction energies for the reactions that take place in local regions, such as calculating the adsorption energies of molecules on transition metal surfaces for modeling surface catalysis.

Formation of SO[formula omitted]H[formula omitted] on the Pt{110}([formula omitted]) surface. A DFT study

Density functional theory is used to calculate energy differences for two surface reactions on the Pt{110}(1×2) surface : SO2↔ SO + O and SO3↔ SO2 + O, first. Formation of SO3 is preferred energetically. Second, several pathways for the formation of SO4H2 are compared from co-adsorbed SO3 and H2O on the mentioned surface. Results reveal an energy difference (endothermic process) of ≈1.5 eV. However, this value decreases to 1.17 eV when the van der Waals interactions are included. Increasing the coverage of H2O to four molecules per SO3 molecule, increases the energy difference to 1.70 eV. However, the energy difference is decreased to 1.06 eV when van der Waals interactions are taken into account in the calculations.

Effects of temperature and loading rate on phase stability and deformation mechanism in metastable V10Cr10Co30FexNi50-x high entropy alloys

Room- and cryogenic-temperature compressive properties for the three V10Cr10Co30FexNi50-x (x = 40, 45, 50) high entropy alloys are investigated under quasi-static and dynamic loading conditions. The face-centered cubic (FCC) stability, which is estimated by the calculation of Gibbs free energy difference between FCC and body-centered cubic (BCC) phases, decreases in increasing order of Fe content. The 40Fe and 45Fe alloys consist of FCC single phase, whereas the 50Fe alloy is composed of a duplex structure with ~95 vol% of body-centered cubic (BCC) lath martensite. Under the quasi-static loading condition at room temperature, the dislocation slip prevails in the 40-at.%-Fe-containing alloy, while the twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP) are activated in the other alloys. The decrease in testing temperature lowers the FCC stability, activating both TWIP and TRIP mode. Under the dynamic loading, the magnitude of TWIP effect enhances, but that of TRIP effect reduces in comparison to the quasi-static loading. The adiabatic heating induced from the dynamic loading increases the FCC stability, thereby resulting in the reduced TRIP effect. Despite the increased stability, the TWIP occurs more actively because the dynamic loading enables the increased flow stress to readily exceed the critical stress required for TWIP. These variations of deformation mechanisms according to the FCC stability, testing temperature, loading rate, adiabatic heating effect, and increased flow stress effect are systematically correlated by the shifting of stability on the slip-TWIP-TRIP mechanism band.

Strategic molecular design of closo-ortho-carboranyl luminophores to manifest thermally activated delayed fluorescence.

In this paper, we propose a strategic molecular design of closo-o-carborane-based donor–acceptor dyad system that exhibits thermally activated delayed fluorescence (TADF) in the solution state at ambient temperature. Planar 9,9-dimethyl-9H-fluorene-based compounds with closo- and nido-o-carborane cages appended at the C2-, C3-, and C4-positions of each fluorene moiety (closo-type: 2FC, 3FC, 4FC, and 4FCH, and nido-type: nido-4FC = [nido-form of 4FC]·[NBu4]) were prepared and characterized. The solid-state molecular structure of 4FC exhibited a significantly distorted fluorene plane, which suggests the existence of severe intramolecular steric hindrance. In photoluminescence measurements, 4FC exhibits a noticeable intramolecular charge transition (ICT)-based emission in all states (solution at 298 K and 77 K, and solid states); however, emissions by other closo-compounds were observed in only the rigid state (solution at 77 K and film). Furthermore, nido-4FC did not exhibit emissive traces in any state. These observations verify that all radiative decay processes correspond to ICT transitions triggered by closo-o-carborane, which acts as an electron acceptor. Relative energy barriers calculated by TD-DFT as dihedral angles around o-carborane cages change in closo-compounds, which indicates that the structural formation of 4FC is nearly fixed around its S0-optimized structure. This differs from that for other closo-compounds, wherein the free rotation of their o-carborane cages occurs easily at ambient temperature. Such rigidity in the structural geometry of 4FC results in ICT-based emission in solution at 298 K and enhancement of quantum efficiency and radiative decay constants compared to those for other closo-compounds. Furthermore, 4FC displays short-lived (∼0.5 ns) and long-lived (∼30 ns) PL decay components in solution at 298 K and in the film state, respectively, which can be attributed to prompt fluorescence and TADF, respectively. The calculated energy difference (ΔEST) between the first excited singlet and triplet states of the closo-compounds demonstrate that the TADF characteristic of 4FC originates from a significantly small ΔEST maintained by the rigid structural fixation around its S0-optimized structure. Furthermore, the strategic molecular design of the o-carborane-appended π-conjugated (D–A) system, which forms a rigid geometry due to severe intramolecular steric hindrance, can enhance the radiative efficiency for ICT-based emission and trigger the TADF nature.

Pure-Blue Fluorescence Molecule for Nondoped Electroluminescence with External Quantum Efficiency Approaching 13%

A pure-blue light-emitting material is one of the key components in the preparation of organic light-emitting diode (OLED) displays. Although high-efficiency blue OLEDs have been realized in therma...

Theoretical Study of Phenoxaphosphine-Based Blue Organic Light-Emitting Diode Exhibiting Thermally Activated Delayed Fluorescence.

We designed novel thermally activated delayed fluorescence (TADF) materials by combining the electron donors spiro[acridine-9,9'-fluorene] (D1) and 9,9-diphenyl acridan (PAC) with the electron acceptor phenoxaphosphine (OPO) unit (2D1-OPO and 2PAC-OPO) and used those property to compare it with that of the reference material using dimethylacridan (Ac) as an electron donor (Ac-OPO) for blue organic light-emitting diodes (OLEDs). To calculate electron distribution of highest occupied molecular orbitals (HOMO), lowest occupied molecular orbital (LUMO), lowest singlet (S1) energy and lowest triplet (T1) excitation states, density functional theory (DFT) and time-dependent DFT calculation have been used. The calculated energy difference (ΔEST) between the S1 and T1 states of 2D1-OPO (0.125 eV) and 2PAC-OPO (0.153 eV) were as small as that of Ac-OPO (0.127 eV). The results showed that 2D1-OPO is a good candidate for blue OLED emitter because it has an emission wavelength of 441.0 nm as well as a sufficiently small ΔEST value and large oscillator intensity value.

13C CPMAS NMR as a Tool for Full Structural Description of 2-Phenyl Substituted Imidazoles That Overcomes the Effects of Fast Tautomerization.

Tautomerization of 2-phenylimidazolecarbaldehydes has not been studied in detail so far, although this process is a well-known phenomenon for imidazole derivatives. That is why we focus our study on a series of 2-phenylimidazolecarbaldehydes and their parent alcohols that were synthesized and studied by detailed 1H and 13C NMR in solution and in the solid state. The apparent problem is that the fast tautomerization impedes the full structural description of the compounds by conventional 13C NMR measurements. Indeed, the 13C NMR spectra in solution exhibit poor resolution, and in most cases, signals from the imidazole ring are not detectable. To avoid this problem, we used 13C CP-MAS NMR as an alternative spectroscopic method for unambiguous spectroscopic characterization of the studied series of 2-phenylimidazoles. The data were analyzed in combination with quantum chemical DFT-GIAO methods by considering the tautomerization process and the intermolecular interactions. The DFT (B3LYP/6-31G(d,p)) calculations allowed to identify and suggest the preferred tautomer in the gas phase and in DMSO solvent, which for alcohols are (2-phenyl-1H-imidazol-4-yl)methanol and its analogs, and for the aldehydes are the 2-phenyl-1H-imidazole-5-carbaldehydes. The gas-phase calculated energy differences between the two possible tautomeric forms are in the range 0.645–1.415 kcal/mol for the alcohols and 2.510–3.059 kcal/mol for the aldehydes. In the DMSO solvent, however, for all compounds, the calculated energy differences go below 1.20 kcal/mol. These data suggest that both tautomeric forms of the studied 2-phenylimidazoles can be present in solution at room temperature. Our data from detailed 2D NMR measurements in the solid state (1H-13C HETCOR and 1H-1H double-quantum coherence MAS NMR) suggested that also in the solid state both tautomers coexist in different crystalline domains. This fact does not obscure the 13C CP-MAS NMR spectra of the studied 2-phenyl substituted imidazoles and suggests this spectroscopic method as a powerful tool for a complete structural description of tautomeric systems with aromatic conjugation.

Photoluminescence studies of the 640nm center in electron irradiated IIa diamond

In this study, a 640 nm center was observed in electron-irradiated type IIa diamond by low-temperature photoluminescence spectroscopy. The origin of the center was explored by temperature dependence analysis. The optical center was at 639.6 nm and adjacent to the negative nitrogen-vacancy center. According to the calculation of energy difference, the splitting of excited states of the nitrogen-vacancy center was excluded as the origin of the 640 nm center. The lattice contraction and electron-phonon coupling model was employed to fit the temperature dependence of the 640 nm center, with all results indicating that the optical center was interstitial defect-related.

Assessment of the SCAN Functional for Spin-State Energies in Spin-Crossover Systems.

The strongly constrained and appropriately normed (SCAN) functional has been tested toward the calculation of spin-state energy differences in a data set of 20 spin-crossover (SCO) systems, ranging from d4 to d7. Results show that the SCAN functional is able to correctly predict the low-spin state as the ground state for all systems, and the energy window provided by the calculations falls in the approximate range of energies that will allow for SCO to occur. Moreover, the SCAN functional can be used in periodic boundary condition calculations, accounting for the effect of collective crystal vibrations and counterions in the thermochemistry of the spin transition. Our results validate this functional as a potential method for in silico screening of new SCO systems at both, molecular and crystal-packed levels.

Ellipsometric determination of anisotropic optical constants of single phase Ga2O3 thin films in its orthorhombic and monoclinic phases

The anisotropic optical constants of high-quality, single crystalline Ga2O3 films in both orthorhombic (ε) and monoclinic (β) phases were obtained from ellipsometry study. The (0001)-oriented ε-Ga2O3 and a (−201) β-Ga2O3 epilayers were grown on (0001) α-Al2O3 substrates by mist-chemical vapor deposition and pulsed laser deposition, respectively. The experimental bandgaps derived from optical constants were found to be related with the allowed optical transitions from valence sub-bands to conduction band minimum in terms of the polarization-selection rules in such asymmetric structures. The pseudo-ordinary (a-b plane) and extraordinary (c axis) optical bandgaps of the ε-Ga2O3 film were estimated to be 4.85 ± 0.02 and 4.76 ± 0.02 eV, respectively. The pseudo ordinary (b axis) and extraordinary (a-c plane) optical bandgaps of the β-Ga2O3 film were estimated to be 4.92 ± 0.02 and 4.57 ± 0.02 eV, respectively. The energy difference between the two bandgaps of the ε-Ga2O3 is about 0.09 eV, which matches the theoretically calculated energy difference (about 0.06 eV) of the highest two valence bands.

Investigation of Thermally Activated Delayed Fluorescence from a Donor-Acceptor Compound with Time-Resolved Fluorescence and Density Functional Theory Applying an Optimally Tuned Range-Separated Hybrid Functional.

Emitters showing thermally activated delayed fluorescence (TADF) in electroluminescent devices rely on efficient reverse intersystem crossing (rISC) arising from small thermal activation barriers between the lowest excited triplet and singlet manifolds. A small donor-acceptor compound consisting of a demethylacridine donor and a methylbenzoate acceptor group is used as a model TADF emitter. The spectroscopic signatures of this system are characterized using a combination of photoluminescence and photoluminescence excitation, and the photoluminescence decay dynamics are recorded between delays of 2 ns and 20 ms. Above T = 200 K, our data provide convincing evidence for TADF at intermediate delays in the microsecond range, whereas triplet-triplet annihilation and slow triplet decay at later times can be observed over the entire temperature range from T = 80 K to room temperature. Moreover, close to room temperature, we find a second and faster up-conversion mechanism, tentatively assigned to reverse internal conversion between different triplet configurations. An interpretation of these experimental findings requires a calculation of the deformation patterns and potential minima of several electronic configurations. This task is performed with a range-separated hybrid functional, outperforming standard density functionals or global hybrids. In particular, the systematic underestimation of the energy of charge transfer (CT) states with respect to local excitations within the constituting chromophores is replaced by more reliable transition energies for both kinds of excitations. Hence, several absorption and emission features can be assigned unambiguously, and the observed activation barriers for rISC and reverse internal conversion correspond to calculated energy differences between the potential surfaces in different electronic configurations.

First-principles study of Zn-doping effects on phase stability and magnetic anisotropy of Ni-Mn-Ga alloys

The effect of Zn doping on Ni-Mn-Ga magnetic shape memory alloy was studied by the first-principles calculations using exact muffin-tin orbital method in combination with the coherent-potential approximation and projector augmented-wave method. Trends in martensitic transformation temperature TM and Curie temperature TC were predicted from calculated energy differences between austenite and nonmodulated martensite, ΔEA−NM, and energy differences between paramagnetic and ferromagnetic state, ΔEPM−FM. Doping upon the Ga-sublattice results in stabilization of martensitic phase which indicates the increase in TM. TC is affected only weakly or slightly decreases, because ΔEPM−FM of martensite does not change significantly with doping. The substitution of Mn atoms by Zn causes the decrease in both TM and TC. Comparing to Cu-doped Ni-Mn-Ga alloys, we predict that doping with Zn results in smaller decrease in TC but also in smaller increase in TM. Moreover, Cu doping upon the Ga-sublattice strongly decreases the magnetic anisotropy energy of martensite, whereas such strong effect was not observed for Zn doping. Based on the calculations of Zn-doped Ni-Mn-Ga alloys we suggest that simultaneous doping with Zn and an element increasing TC can result in significant increase in both transformation temperatures without strong decrease of magnetic anisotropy.

Using Density Matrix Quantum Monte Carlo for Calculating Exact-on-Average Energies for ab Initio Hamiltonians in a Finite Basis Set.

We here apply the recently developed initiator density matrix quantum Monte Carlo (i-DMQMC) to a variety of atoms and molecules in vacuum. i-DMQMC samples the exact density matrix of a Hamiltonian at finite temperature and combines the accuracy of full configuration interaction quantum Monte Carlo (FCIQMC)-full configuration interaction (FCI) or exact energies in a finite basis set-with finite temperature. In order to explore the applicability of i-DMQMC for molecular systems, we choose to study a recently developed test set by Rubenstein and co-workers: Be, H2O, and H10 at near-equilibrium and stretched geometries. We find that, for Be and H2O, i-DMQMC delivers energies with submillihartree accuracy when compared with finite temperature FCI. For H2O and both geometries of H10, we examine the difference between FT-AFQMC and i-DMQMC, which, in turn, estimates the difference in canonical versus grand canonical energies. We close with two discussions: one of simulation settings (initiator error, the interaction picture, and different basis sets), and another of energy difference calculations in the form of specific heat capacity and ionization potential calculations.

Restoration of Wigner’s Sypersymmetry in Heavy and Superheavy Nuclei

Various aspects of restoration of Wigner’s supersymmetry [SU(4) symmetry] in heavy and superheavy nuclei are analyzed by comparing the results of calculations with experimental data. The energy differences between the giant Gamow–Teller and analog resonances ($$E_{\mathrm{G}}$$ and $$E_{\mathrm{A}}$$) are given according to calculations within the theory of finite Fermi systems for 34 nuclei for which experimental data are known. The calculated energy differences $$\Delta E_{\mathrm{G{-}A}}$$ of $$E_{\mathrm{G}}$$ and $$E_{\mathrm{A}}$$ tend to zero in heavier nuclei, demonstrating the restoration of Wigner’s SU(4) symmetry. Also, the isotopic dependence of the Coulomb energy difference between neighboring nuclear isobars is analyzed within the SU(4) approach for more than 400 nuclei in the mass-number range of $$A=5{-}244$$. The restoration of Wigner’s SU(4) symmetry in heavy nuclei is confirmed. It is shown that the restoration of Wigner’s SU(4) symmetry is compatible with the possible existence of an island of stability in the region of superheavy nuclei.

Influence of orthogonal di- and trimerization leading to meso fused BODIPY on linear and NLO properties - TDDFT study and singlet-triplet energy distribution

Orthogonally dimeric meso attached dipyrromethene dyes are examined using computational tools with help of pure, RSH and GH functionals using 6-311++G(d,p) basis set for their steady-state absorption, nonlinear optical characteristics, and singlet-triplet distribution. The vertical excitations of the corresponding oscillator strengths are determined using B3LYP, BHHLYP and CAM―B3LYP using 6-311++G(d,p) method while nonlinear optical properties were established with help of pure, RSH and GH functionals. Dimerization affects the linear polarizability. The insertion of formyl group at 2 and 6 position of BODIPY dyes increases the value of first and second-order hyperpolarizability. The functional CAM―B3LYP is found to be closer in predicting the λabs. The “HOMO-LUMO” energy gap of EA2 was found to be the least which might be attributed to the presence of electron accepting formyl group. The introduction of formyl group and dimerization result in enhancement of dipole moment of these BODIPY dyes. Benchmarking study of proper functionals (pure, GHs and RSHs) to estimate the polarizability values reveal that the lowest value of MSE was found in the case of pure functional for the tHCTH and VSXC (MSE = 0.02 × 10−24 esu). The lowest value of MSE was found in case of GH functional for the M062X (MSE = 0.14 × 10−30 esu) evidence the benchmarking to calculate the first-order polarizability for these dyes. For second-order polarizability (γ0), the lowest value of MSE was found in case of GH for the BMK (MSE = 2.37 × 10−36 esu) evidence the benchmarking for these dyes. The calculated energy difference between E(S1) and E(T1) is following the essential criteria for the singlet fission i.e. E(S1) > 2E(T1) and the difference value found to be positive. The singlet triplet energetic difference (ΔEST) was found to be more precise with CAM―B3LYP and BHHLYP functional compared to B3LYP functional.

Construction of a Range-Separated Dual-Hybrid Direct Random Phase Approximation.

Blending the good performance of the global hybrid PBE0 functional at short-range and the dual-hybrid dRPA75 functional at long range, we propose a new range-separated direct random phase approximation (dRPA75rs), which considerably improves on the accuracy of the calculated reaction energies and barrier heights compared to the parent approaches and provides a good description of noncovalent interactions without any dispersion correction. We also combine the new scheme with spin-component scaling (SCS-dRPA75rs), which enables the accurate calculation of energy differences for processes involving electron pair breaking, such as atomization. The new method scaling as the fourth power of the system size shows a balanced performance on a broad test set involving radicals, transition metal atoms, and heavy atoms, which makes it competitive with the best double-hybrid functionals based on the second-order perturbation theory. According to the results for the homogeneous electron gas, our dRPA75rs method expectedly gives errors for metallic systems similar to the dRPA approach with an additional error cancellation in the case of partial spin polarization.

Approaching the Basis Set Limit of CCSD(T) Energies for Large Molecules with Local Natural Orbital Coupled-Cluster Methods.

Recent optimization efforts and extensive benchmark applications are presented illustrating the accuracy and efficiency of the linear-scaling local natural orbital (LNO) coupled-cluster single-, double-, and perturbative triple-excitations [CCSD(T)] method. A composite threshold combination hierarchy (Loose, Normal, Tight, etc.) is introduced, which enables black box convergence tests and is useful to estimate the accuracy of the LNO-CCSD(T) energies with respect to CCSD(T). We also demonstrate that the complete basis set limit (CBS) of LNO-CCSD(T) energies can be reliably approached via basis set extrapolation using large basis sets including diffuse functions. Where reference CCSD(T) results are available, the mean (maximum) absolute errors of the LNO-CCSD(T) reaction and intermolecular interaction energies with the default Normal threshold combination are below 0.2-0.3 (0.6-1.0) kcal/mol, while the same measures with the Tight setting are 0.1 (0.2-0.5) kcal/mol for all the tested systems including highly complicated cases. The performance of LNO-CCSD(T) is also compared with that of other popular local CCSD(T) schemes. The exceptionally low hardware requirements of the present scheme enables the routine calculation of benchmark-quality energy differences within chemical accuracy of CCSD(T)/CBS for systems including a few hundred atoms. LNO-CCSD(T)/CBS calculations can also be performed for more than 1000 atoms with 45,000 atomic orbitals using a single, six-core CPU, about 100 GB memory, and comparable disk space.

Deep-Blue Thermally Activated Delayed Fluorescence Emitters Containing Diphenyl Sulfone Group for Organic Light Emitting Diodes.

Novel blue thermally activated delayed fluorescence (TADF) emitters, D1-DPS and D2-DPS, were designed and synthesized. Diphenyl sulfone (DPS) group functioned as a common acceptor, and it combined with each of two different spiro-acridine groups, D1 and D2. The calculated energy differences (ΔEST) of the singlet and triplet excited states of D1-DPS (0.062 eV) and D2-DPS (0.128 eV) had sufficiently small ΔEST values, which is favorable in the thermally activated reverse intersystem crossing (RISC) process from the T1 state to the S1 state. A device doped 10 wt% of D2-DPS with ADN host material, obtained 5.05% of external quantum efficiency with deep-blue emission having CIExy coordinates of (0.152, 0.065). The results showed that these molecules are promising host-free TADF deep-blue emitters by inhibiting concentration quenching.

Stereoselective bioactivity, toxicity and degradation of the chiral triazole fungicide bitertanol.

The chiral pesticide bitertanol has been widely used in the prevention and treatment of fungal diseases on many crops. However, research on bitertanol at the stereoisomer level has not been reported. Here, we study the stereoselective bioactivity, toxicity, and degradation of this pesticide under laboratory and field conditions. (1S,2R)-Bitertanol was the most effective stereoisomer, showing 4.3-314.7 times more potent bioactivity than other stereoisomers against eight target pathogenic fungi. (1S,2R)-Bitertanol showed 10.2 times greater inhibition of Botrytis cinerea spore germination than (1R,2S)-bitertanol. According to the receptor-drug docking results, the distances from the nitrogen atom in the heterocycle of (1S,2R)-, (1R,2S)-, (1R,2R)-, and (1S,2S)-bitertanol to the central Fe + atoms in the ferriporphyrin were 2.5, 3.8, 2.6, and 3.8Å, respectively. (1S,2S)-Bitertanol was 1.6-2.7 times more toxic than (1R,2R)-bitertanol to Chlorella pyrenoidosa. The half-lives of (1R,2S)-, (1S,2R)-, (1R,2R)-, and (1S,2S)-bitertanol were 3.7, 4.1, 4.1, and 4.8 d, respectively, in tomato. The stereoselective bioactivity, toxicity, and degradation for bitertanol were first studied here. (1S,2R)-Bitertanol was a high efficiency and low toxicity stereoisomer. Moreover, the stereoselective bioactivity among all stereoisomers correlated with the binding distances and calculated energy differences between stereoisomers and the target protein. This study also provides a foundation for a systematic evaluation of bitertanol at the stereoisomer level. © 2019 Society of Chemical Industry.