C4F7N with excellent insulation performance has been proposed to replace the traditional SF6 as a new insulating medium in power equipment. In the present study, the molecular structure and radiative efficiency (RE) of C4F7N are calculated and compared with SF6 based on DFT calculation. The decomposition of pure C4F7N and the basic interactions between C4F7N and hydroxyl radical in the constructed co-crystal of C4F7N-H2O have been simulated by applying Monte-Carlo calculation and Car-Parrinello molecular dynamics (CPMD) method, in order to obtain reasonable and full-scale atmospheric dissociation processes. Then the detailed decomposition pathways are learned with DFT method of M062X. The rate constants of different pathways are further applied for calculating the atmosphere lifetime of C4F7N, to evaluate the possibility of applying it as an alternative gas of SF6 in power equipment. All the atmospheric chemical behaviours are determined by electronic structure and reflected by the decomposition pathways of C4F7N with interacting with hydroxyl radicals. Rather than traditional hypothesizing reaction models, this study provides a reasonable and practicable method to evaluate more alternative protective gas for understand the greenhouse effect.
In this work, we propose a technique for the use of fermionic neural networks (FermiNets) with the Slater exponential Ansatz for electron-nuclear and electron-electron distances, which provides faster convergence of target ground-state energies due to a better description of the interparticle interaction in the vicinities of the coalescence points. Our analysis of learning curves indicates on the possibility to obtain accurate energies with smaller batch sizes using arguments of the bagging approach. In order to obtain even more accurate results for the ground-state energies, we propose an extrapolation scheme for estimating Monte Carlo integrals in the limit of an infinite number of points. Numerical tests for a set of molecules demonstrate a good agreement with the results of the original FermiNets approach (achieved with larger batch sizes than required by our approach) and with results of the coupled-cluster singles and doubles with perturbative triples (CCSD(T)) method that are calculated in the complete basis set (CBS) limit.
Experimental and theoretical studies show that two-dimensional (2D) materials have great potential applications in the fields of optoelectronics, semiconductors and spintronic devices. Based on the First Principles, the stability, band structure, electronic properties and optical properties of hydrogenated C3B, a new graphene like two-dimensional (2D) material, are studied in this paper. The results show that: firstly, with the increase of hydrogenation degree, the sp2 orbital hybridization in C3B structure gradually transits to a more stable sp3 mode, and the valence band energy near the Fermi level decreases; Secondly, adsorbed H atoms can regulate the bandgap of C3B. When the number of adsorbed H is even, C3B structure behaves as a semiconductor, and meanwhile the bandgap increases. When H atoms is odd, C3B is easy to show metallicity; Finally, the main absorption peak of the optical absorption spectrum decreases first and then increases with the increase of H concentration. The law of the secondary absorption peak is opposite to the main peak. When the ratio of hydrogenation is 50%, an obvious secondary absorption peak appears. This study confirms that hydrogenation is an effective way to regulate the electronic properties of materials, which can expand the application of 2D material C3B in optoelectronic devices.
A proper benchmarking on the properties of HF and its dimer inside C60 using density functional theory (DFT) based approaches is presented. For this purpose, 10 different DFT functionals following Jacob’s Ladder have been chosen. Geometrical parameters, viz., bond length, bond angle, etc., and dipole moment have been computed. Two types of orientations, viz., L-shaped and anti-parallel of (HF)2 inside C60 are considered, the latter with an extremely short hydrogen bond. HF bond lengths are elongated upon encapsulation in comparison to its free state analogue. The calculated stability of HF@C60 is functional dependent whereas, (HF)2C60 is thermodynamically unstable for all the functionals. The kinetic stability of (HF)2@C60 is observed through ADMP simulation at 300K temperature. The red shift in HF stretching frequencies is noticed in all cases. NCI analysis exhibits a non-covalent type interaction between HF dimer and the C60 cage. The total interaction energy is found to be negative for HF@C60. EDA analysis showed a high value of repulsive ΔEpauli which makes the (HF)2@C60 system unstable except for the functional BP86-D3 of GGA family. Furthermore, QTAIM analysis is performed and confirmed the presence of (3, -1) bond critical point along the hydrogen bond region for L-shaped (HF)2C60.
In this account we report an implementation of the quantum trajectory-guided adaptive Gaussian (QTAG) method in a modular open-source Libra package for quantum dynamics calculations. The QTAG method is based on a representation of wavefunctions in terms of a quantum trajectory-guided adaptable Gaussians basis and is generalized for time-propagation on multiple coupled surfaces to be applicable to model nonadiabatic dynamics. The potential matrix elements are evaluated within either the local harmonic or bra-ket-average (linear) approximations to the potential energy surfaces, the latter being a more practical option. Performance of the QTAG method is demonstrated and discussed for the Holstein and Tully models, which are the standard benchmarks for method development in the area of nonadiabatic dynamics.
Density functional theory (DFT) was used to calculate the most stable structures of Gen (n=2-5) clusters as well as the adsorption energies of Gen (n=2-5) clusters after adsorbing single water molecule. The calculation of the reaction paths between Gen (n=2-5) and single water molecule shows that water molecule can react with Gen (n=2-5) clusters to dissociate to produce hydrogen, and O atoms mix with the clusters to generate GenO (n=2-5). According to the energy change of the reactions, the Ge2 cluster is the most efficient among Gen (n=2-5) clusters reacting with single water molecule. The NPA and DOS respectively proved that the Ge atoms in the product don’t reach the highest valence, and it was jointly predicted that GenO (n=2-5) might continue to react with more water molecules. Our findings contribute to better knowledge of Ge’s chemical reactivity, which could aid in the development of effective Ge-based catalysts and hydrogen-production methods.
Studies have shown that fluvoxamine can be useful in preventing the spread of Covid-19 disease (in the early stages of the disease) by strengthening the body’s immune system. For this purpose, in this work, the structural and electronic properties of fluvoxamine drug were investigated using quantum theory of atom in molecule (QTAIM) and Density-functional theory (DFT) at B3LYP-DFT/6-311G+ (at presence of water as solvent and the CPCM model) computational level. Also, in order to improve the electronic/pharmaceutical properties, the effect of electron donor/acceptor groups of NO2 and NH2 on fluvoxamine was studied. According to the results, electronic properties changed significantly in the presence of the NO2 group. So that (in the presence of NO2) cohesive energy, energy gap, dipole moment, adsorption energy, antioxidant properties, and recovery time improved by 20%, 70%, 84%, 48%, 48%, and 46% respectively. Although the electronic properties were improved in the presence of the NH2 group, the effect of the NO2 functional group was more noticeable. Therefore, it is expected that the presence of the NO2 electron-acceptor electron group will improve its medicinal function by changing the electronic properties of the drug fluvoxamine.
In order to quantify the site-dependent correlation strengths in terms of the quasi-particle weights and the occupation numbers of 5f electrons in alpha phase plutonium metal with eight crystallographically nonequivalent atomic sites Pun (n=1~8), we perform a first principles calculation by using a many-body method merging density functional theory (DFT) with dynamical mean-field theory (DMFT) plus the relativistic and correlation effects. The quasi-particle weight, the electronic spectrum function, the hybridization function, as well as the occupation number of Pu 5f electrons all suggest that Pu1 and Pu8 atoms have the most itinerant and the most localized 5f electrons, respectively, while the other atoms Pun (n=2~7) exhibit an intermediate correlation strength. The quasi-particle weights demonstrate that only the jj or intermediate coupling scheme is more appropriate for Pu 5f electrons in comparison with the Russel-Saunders (LS) scheme. The electronic spectrum function and the occupation analysis establish that Pu 5f electrons simultaneously have dual itinerant and localized regimes with average 5f occupation numbers of nf between 4.8994 and 4.9628, which are mainly composed of 5f4, 5f5 and 5f6 configurations, irrespective of different atomic sites. Finally, we also estimate the so-called quasi-particle band structure to directly compare with an experimental angle-resolved photoemission spectrum (ARPES).
Nitric oxide (NO) is a ubiquitous signaling molecule in a variety of physiological and pathological process in living organisms. A two-photon probe, i.e., 2-acetyl-6-dialkylaminonaphthalene as the reporter and an o-diaminobenzene as the reaction site for NO, linked by prolinamide (ANO1), has been synthesized. Based on the experimental study, five other two-photon probes have been designed by substituting the naphthalene fluorophore in ANO1 with the luciferin analogue (ANO2), pyrene (substitution at 1,6-position, ANO3, and 2,7-position, ANO3’), fluorene (ANO4), and boron-dipyrromethene (ANO5) units. DFT/TDDFT studies have been conducted on both experimental two-photon probe ANO1 and designed ANOn (n=2–5). Our results indicated that for designed probes, both absorption and emission spectra show red shifts compared with ANO1. The one- and two-photon absorption band positions as well as the emission wavelength do have no significant change for each probe before and after reaction with NO. However, the fluorescence intensities are enhanced after reaction with NO. ANO3 and ANO4 have large two-photon absorption cross sections. Furthermore, analysis of molecular orbitals is exhibited to interpret the photoinduced electron transfer mechanism between the donor and acceptor.
Geometries and electronic properties of selfassembled (InN)12n (n=1-9) nanosheets or nanowires are investigated at the PBE1PBE level. The growth patterns of semiconductor InN nanocrystal are revealed. Relative stabilities of (InN)12n (n=1-9) are studied. The even-numbered (InN)12n (n is even) nanoclusters have stronger stabilities than the neighboring odd-numbered (InN)12n ones. The particular stable geometries are assigned as the (InN)48 nanosheet for selfassembled film nanomaterials. The calculated energy gaps exhibit even-odd oscillation and reveal that (InN)12n (n=1-9) semiconductor nanoclusters are apparently good optoelectronic or energy nanomaterials; Furthermore, (InN)12n nanoclusters with energy gaps at the visible regions have potential applications in microelectronic and optoelectronic nanodevices. The slightly varied energy gaps for (InN)12n nanowires reveals they maintain individual (InN)12 properties. The calculated charge-transfers for (InN)12n (n=1-9) reflect that their ionic bonding enhances the stabilites of nanoclusters and that ionic bonding in (InN)12n (n=1-9) nanoclusters exists with covalent.
A search has been conducted, employing ab initio molecular orbital theory, for potential tetrel-bonded complexes between the fluorinated methanes methyl fluoride, difluoromethane and fluoroform, and the related hydrides ammonia, water, hydrogen fluoride, phosphine, hydrogen sulfide and hydrogen chloride. Eleven such complexes have been identified, six containing CH3F and five CH2F2. The complexes are typically less strongly bound than their hydrogen-bonded counterparts, and the interaction energies vary in a consistent way with the periodic trend of the electron donors. The intermolecular separations and changes of the relevant intramolecular bond lengths, the wavenumber shifts of the critical vibrational modes, and the extents of charge transfer for the atoms most closely involved in the interactions correlate, by and large, with the strengths of interaction.
By employing the Nikiforov-Uvarov functional analysis (NUFA) method, we solved the radial Schrodinger equation with the shifted Morse potential model. The analytical expressions of the energy eigenvalues, eigenfunctions and numerical results were determined for selected values of the potential parameters. Variations of different thermodynamic functions with temperature were discussed extensively. Different quantum information theories including Shannon entropy, Fisher information and Fisher-Shannon product of the shifted Morse potential were investigated numerically and graphically in position and momentum spaces for ground and first excited states. The quantum information theories considered satisfied their corresponding inequalities including Bialynicki–Birula–Mycielski, Stam–Cramer–Rao inequalities and the Fisher–Shannon product relation.
Possible theoretical basis for the hypothesis of prohibition of some electron configurations in atoms and molecules presented by one of the authors earlier is considered. Existence of such prohibited configurations follows from the wave function antisymmetry of atoms and molecules. Our hypothesis is as follows: the configurations, in which the potentials of any two electrons with the same spins are equal, are forbidden. If the hypothesis comes true, it will be possible to find the nodal surfaces of many-electron wave functions for atoms and molecules analytically a priori.
A series of cyclometalated platinum(II) complexes with aromatic ligands, such as pyridyl, pyrimidinyl and pyrazolate, were investigated with theoretical calculations. To investigate the relationship between ligands with molecular orbital, molecular rigidity, electroluminescent properties and spectroscopic properties, the electrostatic potential (ESP), density-of-states (DOS), root mean squared displacement (RMSD) were calculated. On the basis of calculated absorption and phosphorescence data, the analysis of “hole” and “electron” have also been performed. From the RMSD calculations, complex 3 shows significant structural distortions on S1 state and it may be applied in thermal activation delayed fluorescence (TADF) materials. The electroluminescent properties calculations show that complex 1 is suitable for hole transport material and complex 4 can be applied in electron transport material.
Half heusler compounds have gained attention due to their excellent properties and good thermal stability. In this paper, using first principle calculation and Boltzmann transport equation, we have investigated structural, electronic, mechanical and thermoelectric properties of PdXSn (X=Zr,Hf) half Heusler materials. These materials are indirect band gap semiconductors with band gap of 0.52 (0.44) for PdZrSn (PdHfSn). Calculations of elastic and phonon characteristics show that both materials are mechanically and dynamically stable. At 300K the magnitude of lattice thermal conductivity observed for PdZrSn is 15.16 W/mK and 9.53 W/mK for PdHfSn. The highest ZT value for PdZrSn and PdHfSn is 0.32 and 0.4 respectively.
Hydrogen reduction of tungsten oxide is currently the most widely applied ultrafine tungsten powder production process. The process has the advantage of short, pollution free and simple production equipment. But it is difficult to effectively control the morphology and particle size of the tungsten powder because of lacking in-depth understanding of the dynamic mechanism of the process. The first-principles calculations are carried out to explore the diffusion and internal adsorption of hydrogen on the WO-terminated surface of WO3 based on the density functional theory. The results show that hydrogen can diffuse from the WO terminal surface to the inside of WO3, the activation energy of diffusion is 46.682 Kcal/mol. It’s preferable for hydrogen to diffuse from the surface to the inside than diffuse within the WO3 lattice. The adsorption energy of hydrogen on the WO termination surface of WO3 is 15.093 Kcal/mol, the adsorption energy of hydrogen inside the WO termination surface of WO3 is 14.116 Kcal/mol, which means the hydrogen is easier to adsorb inside the WO3 lattice.
Quantum chemical calculations have been performed on B3 ring stabilized Y-Y interaction (Y = Be, Mg, Ca) to understand the possibility of binuclear sandwich type complex formation. Calculations indicate single reference character of the studied systems. The complexes have been found to be stable towards dissociation into different fragments. Thermodynamic consideration also indicates the favourability of their formation. Increase in aromaticity of the parent B3 ring upon complexation is observed which is expected to provide extra stability to the complexes.
A two-sublattice decorated Blume-Capel ferrimagnet has been investigated using the mean field theory. Interesting behaviors of long-range order are obtained depending on particular magnitudes of magnetocrystalline anisotropies for both sublattices sites. Distinguishable features have been discovered in two-dimensional decorated lattice consisting of spin-5/2 and decorating spin-7/2 ions on the bonds. It is found the present system shows two ferrimagnetic compensation temperatures. However, one compensation temperature for different or fixed values of decorated magnetic anisotropies with the values of J1=-0.5 , J2=-1.0 , or with J1=-1.0 , J2=-0.5, has been induced, respectively. The magnetization behavior in the (M,DB/IJ2I) space has not already been considered showing the crystalline anisotropy dependence of total magnetization remanences. Besides, the variations of net magnetizations versus the decorated crystal fields, i.e., in the(M,DA/IJ2I) space, have been done, with J1=-0.5, J2=-1.0 , for various values of T=2.0, 2.5,3.0 , respectively.