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: <i>Ab initio</i> and Monte Carlo approaches
摘要： The effects of nonmagnetic impurity doping on magnetic and ferroelectric properties of multiferroic delafossite CuCrO2 are investigated by means of density functional theory calculations and Monte Carlo simulations. Density functional theory calculations show that replacing up to 30% of Cr3+ ions by Ga3+ ones does not significantly affect the remaining Cr-Cr superexchange interactions. Monte Carlo simulations show that CuCr1?xGaxO2 preserves its magnetoelectric properties up to x ≈ 0.15 with a spiral ordering, while it becomes disordered at higher fractions. Antiferromagnetic transition shifts towards lower temperatures with increasing x and eventually disappears at x ≈ 0.2. Our simulations show that Ga3+ doping increases the Curie-Weiss temperature of CuCr1?xGaxO2, which agrees well with experimental observations. Moreover, our results show that the incommensurate ground-state configuration is destabilized by Ga3+ doping under zero applied field associated with an increase of frustration. Finally, coupling between noncollinear magnetic ordering and electric field is reported for x ≤ 0.15 through simulating P -E hysteresis loops, which leads to ferroelectricity in the extended inverse Dzyaloshinskii-Moriya model.
关键词： CuCrO2,multiferroic,Monte Carlo simulations,ferroelectric properties,magnetic properties,density functional theory,delafossite,Ga doping
更新于2025-09-23 15:21:01
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High-Pressure Electronic Structure and Optical Properties of N-Doped ZnO
摘要： The electronic structures and optical properties of N-doped ZnO under high pressure have been investigated using first-principles methods. The pressure effects on the lattice parameters, electronic band structures, and partial density of states (PDOS) of crystalline N-doped ZnO are calculated up to 8 GPa. The lattice parameters a, and c are decreases by 0.062 and 0.091 ?, respectively. Moreover, the evolution of the dielectric function, absorption coefficient (α(ω)), reflectivity (R(ω)), and the real part of the refractive index (n(ω)) at high pressure are also presented.
关键词： N-doped ZnO,density functional theory,optical properties,high pressure
更新于2025-09-23 15:21:01
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Ancillary ligand increases the efficiency of heteroleptic Ir-based triplet emitters in OLED devices
摘要： The excellent contrast ratio, visibility, and advantages in producing thin and light displays let organic light emitting diodes change the paradigm of the display industry. To improve future display technologies, higher electroluminescence efficiency is needed. Herein, the detailed study of the non-radiative decay mechanism employing density functional theory calculations is carried out and a simple, general strategy for the design of the ancillary ligand is formulated. It is shown that steric bulk properly directed towards the phenylisoquinoline ligands can significantly reduce the non-radiative decay rate.
关键词： photoluminescence quantum yield,non-radiative decay,OLED,Ir(III)-complexes,density functional theory
更新于2025-09-23 15:21:01
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Photophysical Properties of Nitrated and Halogenated Phosphorus Tritolylcorrole Complexes: Insights from Theory
摘要： The photophysical properties of a series of nitrated and halogenated phosphorus tritolylcorrole complexes were studied in dichloromethane solvent by using the density functional theory. Particular emphasis was given to the absorption spectra, the energy gap between the excited singlet and triplet states, and the magnitude of the spin-orbit couplings for a series of possible intersystem crossing channels between those excited states. The proposed study provides a better description of the photophysical properties of these systems while giving insights into their possible use as photosensitizers in photodynamic therapy.
关键词： photodynamic therapy,phosphorus tritolylcorrole,heavy atom effect,density functional theory,spin-orbit coupling
更新于2025-09-23 15:21:01
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Designing indenothiophene-based acceptor materials with efficient photovoltaic parameters for fullerene-free organic solar cells
摘要： Non-fullerene small molecular acceptors (NFSMAs) exhibit promising photovoltaic performance which promoted the rapid progress of organic solar cells (OSCs). In this study, an attempt is done to explore indenothiophene-based high-performance small molecular electron acceptors for organic solar cells. We have designed five acceptor molecules (M1–M5) with strong donor moiety indenothiophene linked to five different end-capped group acceptor moieties: diflouro-2-methylene-3-oxo-2,3-dihydroindene-1-ylidene)malononitrile (A1), 1-(dicyanomethylene)-2-methylene-3-oxo-2,3-dihydro-1H-indene-5,6-dicarbonitrile (A2), methyl-6-cyano-3-(dicyanomethylene)-2-methylene-1-oxo-2,3-dihydro-1H-indene-5-carboylate (A3), 2-(6-cyano-5-fluoro-2-methylene-3-oxo-2,3 dihydro-1H-indene-1-ylidene)malononitrile (A4), and (Z)-methyl 3-(benzo [c][1,2,5]thiadiazol-4-yl)-2-cyanoacrylate (A5) respectively. The structure–property relationship was studied and effects of structural modification on the optoelectronic properties of these acceptors (M1–M5) were determined systematically by comparing it with reference molecule R, which is recently reported as excellent non-fullerene-based small acceptor molecule. Among all designed molecules, M5 is proven as a suitable candidate for organic solar cell applications due to better photovoltaic properties including narrow HOMO-LUMO energy gap (2.11 eV), smallest electron mobility (λe = 0.0038 eV), highest λmax values (702.82 nm in gas) and (663.09 nm in chloroform solvent) and highest open-circuit voltage (Voc = 1.49 V) with respect to HOMOPTB7-Th–LUMOacceptor. Our results indicate that introducing more end-capped electron-accepting units is a simple and effective alternative strategy for the design of promising NFSMAs. This theoretical framework also proves that the conceptualized NFSMAs are superior and thus are recommended for the future construction of high-performance organic solar cell devices.
关键词： Photovoltaic properties,Indenothiophene,Density functional theory (DFT),Non-fullerene acceptor materials,Organic solar cells (OSCs)
更新于2025-09-23 15:21:01
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Chromophores in cellulosics, XVIII. Degradation of the cellulosic key chromophore 5,8-dihydroxy-[1,4]-naphthoquinone under conditions of chlorine dioxide pulp bleaching: a combined experimental and theoretical study
摘要： DHNQ is one of the key chromophores occurring in all types of aged cellulosics. This study investigates the degradation of DHNQ by chlorine dioxide at moderately acidic (pH 3) conditions, corresponding to the conditions of industrial bleaching ("D stage"). The degradation involves three major pathways. As initial reaction, a hydrogen transfer from DHNQ to chlorine dioxide via a PCET mechanism occurs to form a radical DHNQ(cid:2) and chlorous acid. DHNQ(cid:2) is then attacked by water to give a pentahydroxynaphthalene radical PHN(cid:2) that is stabilized by strong delocalization of the non-paired electron into its aromatic ring. PHN(cid:2) immediately disproportionates to give the observable intermediate 1,2,4,5,8-pentahydroxynapththalene (I), which was comprehensively con?rmed by NMR and MS (path A). In the presence of excess ClO2, I is immediately further oxidized into acetic acid, glycolic acid, oxalic acid and CO2 as the ?nal, stable, and non-colored products (path C). In the absence of excess ClO2, elimination of water from I regenerates DHNQ (path B), so that at roughly equimolar DHNQ/ClO2 ratios ClO2 is fully consumed while a major part of DHNQ is recovered. To avoid such DHNQ "recycling" under ClO2 consumption—and to completely degrade DHNQ to colorless degradation products instead—ClO2 must be applied in at least ?vefold molar excess relative to DHNQ.
关键词： Density functional theory (DFT),Ab initio calculations,Yellowing,Cellulose,Brightness,Chromophores,5,8-dihydroxy-[1,4]-naphthoquinone,Chlorine dioxide,Brightness reversion,Pulp bleaching
更新于2025-09-23 15:21:01
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POM-based dyes featured rigidified bithiophene ?? linkers: Potential high-efficient dyes for dye-sensitized solar cells
摘要： A series of POM-based dyes with triphenylamine electron donor group, cyanoacrylic acid electron acceptor group and different π linkers of thiophene derivatives are systematically investigated to analyze the influence of rigidified bithiophene with fastening atoms (C and N) on the performance of dye-sensitized solar cells (DSSCs) based on density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. The interfacial electron transfer (IET) processes are evaluated, which is less investigated previously. We can see that the electron in dyes 2, 4 and 5 are almost completely injected after 100 fs, thus leading to the fast IET. Dye 2 not only has lower interaction energy for most stable dimer configuration than dye 1, but also has larger short-circuit photocurrent density JSC and open-circuit photovoltage VOC, resulting from the insertion of POM group. Compared with dye 3 containing 2,2'-bithiophene π linker, its two counterparts (dyes 4 and 5) with rigidified bithiophene π linkers tend to accelerate IET process as well as retard the electron recombination, thus improve the performance of DSSCs. In particular, dye 4 with rigidified bithiophene π linker fastening by C atom would obtain the larger JSC and VOC than that of dye 5 with N atom rigidified bithiophene π linker.
关键词： rigidified bithiophene,POM-based dyes,interfacial electron transfer,dye-sensitized solar cells,density functional theory
更新于2025-09-23 15:21:01
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Synthesis, crystal structure analysis, spectral characterization and nonlinear optical exploration of potent thiosemicarbazones based compounds: A DFT refine experimental study
摘要： The thiosemicarbazones have exciting biological and nonlinear optical (NLO) applications. The present study reports detail experimental and computational studies of three novel ferrocene-substituted thiosemicarbazones: (E/Z)-4-(4-chlorobenzyl)-1-(1-ferrocenyl-ethyl)thiosemicarbazone (2) and (E/Z)-4-benzyl-1-(1-ferrocenylethyl)thiosemicarbazones (1) and (E/Z)-4-(2-bromo benzyl)-1-(1-ferrocenylethyl)thiosemicarbazone (3). These compounds were synthesized and resolved into their single crystal structures for the estimation of unit cells, space groups, bond angles and bond lengths. Chemical structures of 1–3 were further characterized spectroscopically employing nuclear magnetic resonance technique (1H NMR), infrared (FT-IR), mass and UV–Visible studies. Computational studies of 1–3 were performed using density functional theory (DFT) tools at M06 level of theory and 6–31 + G(d,p) basis set combination to gain the optimized geometry. A good correlation was found between experimental SC-XRD structures and DFT optimized geometries. Electronic properties including natural bond orbital (NBO) analysis, frontier molecular orbitals (FMOs) analysis, spectroscopic FT-IR data and NLO properties were calculated using same M06/6–31 + G(d,p) level of theory. NBO analysis confirmed the formation of charge separation state due to successful migration of electrons from donor to acceptor unit through π-bridge. Global reactivity parameters were estimated using energies of FMOs which described that 1–3 are chemically hard and stable molecules. Vertical electronic transition states were calculated using time-dependent DFT (TDDFT) at same level of theory. NLO properties of 1–3 were computed 5.77, 3.48 and 8.93 times greater than the standard urea molecule respectively. Two-state model confirmed the potential of synthesized molecules as NLO candidates.
关键词： Frontier molecular orbital,Ferrocene-substituted thiosemicarbazones,Spectroscopic data,Crystal structures,Non-linear optical properties,Density functional theory
更新于2025-09-23 15:21:01
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Theoretical Investigation of Azobenzene-Based Photochromic Dyes for Dye-Sensitized Solar Cells
摘要： Two donor-π-spacer-acceptor (D-π-A) organic dyes were designed as photochromic dyes with the same π-spacer and acceptor but di?erent donors, based on their electron-donating strength. Various structural, electronic, and optical properties, chemical reactivity parameters, and certain crucial factors that a?ect short-circuit current density (Jsc) and open circuit voltage (Voc) were investigated computationally using density functional theory and time-dependent density functional theory. The trans-cis isomerization of these azobenzene-based dyes and its e?ect on their properties was studied in detail. Furthermore, the dye-(TiO2)9 anatase nanoparticle system was simulated to understand the electronic structure of the interface. Based on the results, we justi?ed how the trans-cis isomerization and di?erent donor groups in?uence the physical properties as well as the photovoltaic performance of the resultant dye-sensitized solar cells (DSSCs). These theoretical calculations can be used for the rapid screening of promising dyes and their optimization for photochromic DSSCs.
关键词： azobenzene,dye-sensitized solar cells,density functional theory
更新于2025-09-23 15:21:01
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Assessing the Performance of Cobalt Phthalocyanine Nanoflakes as Molecular Catalysts for Li-Promoted Oxalate Formation in Li–CO <sub/>2</sub> –Oxalate Batteries
摘要： Removal of O2 molecules from the cathode environment in the Li-based battery has led to introduction of the Li?CO2 battery as the novel and promising source of energy storage. In spite of CO2 capture through the reversible reaction between Li atoms and CO2 molecules at the cathode, the performance of the Li?CO2 battery is hampered by formation of the Li2CO3 insulating product in the discharge process and its di?cult decomposition in the charging process. Hereby, we explore the possible improvement of the performance of the Li?CO2 battery through replacement of Li2CO3 by Li2C2O4 as the discharge product. This is achieved by systematic addition of Li and CO2 to a cobalt phthalocyanine (CoPc) nano?ake employed as the molecular catalyst in the cathode of the Li?CO2 battery by means of computational density functional theory-based methods. The present results predict high adsorption energy of the CO2 molecules (?2.16 eV), low Li-intercalation voltage (1.45 V), reveal the important and constructive in?uence of the electrolyte (dimethyl sulfoxide) on the adsorption and decomposition energies and Li-intercalation voltage, and suggest a through-space electron transfer mechanism for the formation of the Li2C2O4 product on the CoPc nano?ake. Moreover, the high electron a?nity of the CoPc nano?ake along with the suitable thermodynamics and kinetics of electron transfer from the CoPc nano?ake to the CO2 molecules during the formation of the Li2C2O4 product con?rm the potential abilities of the CoPc nano?ake to be used in the Li?CO2 battery. Therefore, present results provide a sound assessment of the capability of the CoPc nano?ake as a cathode material in the Li?CO2 battery and show that this provides a possible and e?ective solution to improve the performance of the Li?CO2 battery and to introduce new Li?CO2?oxalate batteries.
关键词： Li?CO2 battery,cobalt phthalocyanine,electron transfer mechanism,density functional theory,molecular catalyst
更新于2025-09-23 15:21:01