R1216 is thermally decomposed and reacts with free radicals in a flame to form a series of products. Some reactive radicals (such as CF₃· radicals) continue to react with H· and OH· radicals required to maintain the flame; another part of the products continues to decompose into new substances, such as non-flammable perfluoroalkanes and perfluoroalkenes.

Abstract

Due to the severe damage of Halon to the stratospheric ozone layer, the urgent need for substitutions for Halon has driven the search for potential alternatives. As a perfluoroolefin substance, R1216 (1,1,2,3,3,3-hexafluoro-1-propene) has a similar chemical structure to the widely used 2-bromo-3,3,3-trifluoro-1-ene (CF₃CBrCH₂, 2-BTP) extinguishants. This study revealed the thermal decomposition and fire-extinguishing performance of R1216 using theoretical calculations and experimental measurements. It was found that R1216 has high thermal stability and does not decompose at 600°C, and not only achieves the purpose of chemical extinguishment by generating perfluoroalkanes, perfluoroolefins and CF₃· radicals that can capture H· and OH· radicals in the flame to interrupt the chain reactions of combustion, but also achieve the goal of cooling by absorbing heat through bond breaking. A combination of physical and chemical inhibition makes R1216 ideal for fire suppression (6.78 and 7.40 vol% for methane and propane flames, respectively). R1216 does not contain Br· and has a global warming potential of 0, which is more environmentally friendly. These findings suggested that R1216 may be a potential Halon substitute with promising applications and deserved further evaluation.

Metastable aluminum boride Al_1.28B has been studied theoretically for the first time. The calculated formation enthalpy of AlB₂ is −3.6 kcal/mol. The calculated formation enthalpy of Al_1.28B varies within 4.8 ± 0.4 kcal/mol. The elastic energy required to for the formation of Al_1.28B is lower than for AlB₂. The structural state of the initial components (Al and B) determines the composition of the reaction products.

Abstract

Aluminum borides have significant practical interest as energetic additives to fuels, explosives and propellants due to their favorable thermodynamic and kinetic characteristics. Density functional theory calculations with periodic boundary conditions have been performed to evaluate the enthalpy of formation of two aluminum borides: the well-known aluminum diboride AlB₂ and the metastable Al_1.28B phase, which precedes the formation of AlB₂ during heat treatment of mechanically activated composite aluminum-boron powders, as well as aluminum ion-implanted with boron. The calculated formation enthalpy of AlB₂ is −3.6 kcal/mol, which agrees well with estimates from literature. The enthalpy of formation of Al_1.28B, calculated for the first time, is 4.8 ± 0.4 kcal/mol. To understand the prerequisites for the formation of Al_1.28B observed in experiments, the enthalpy of formation of supersaturated solid solutions of B in Al has been evaluated. The reasons for the preferential formation of the metastable Al_1.28B phase over the thermodynamically stable AlB₂ phase are discussed.

Artificial intelligence, AI, and human intelligence, HI, is analysed from a quantum chemical perspective. Carbon prejudice versus ‘computation all the way down’ is compared with reference to substrate dependent disciplines, such as chemistry and biology. The self-referential law of nature, starting at the microscopic level, will address the complexity of living systems, from atomic-molecular levels to biological processes all the way up to our present acumen.

The author is indebted to the UCL Faculty of Brain Sciences for the permission to use this image.

Abstract

The present rate of growth of powerful AI systems motivates an accurate comparison between the notion of computers and the workings of natural sciences. Statements such as “intelligence doesn't require flesh, blood or carbon atoms” or “it's computation all the way down” incite a substrate-independent view, providing shortcuts for Darwinian evolution and the possible appearance of sentient machines. This view is discussed and contrasted from a quantum chemical perspective. The qualitative difference between the developed AI and the evolved HI is recognized and the importance of a material constituent, formulated in terms of energy-temperature, conjugate to an immaterial ingredient, in the context of time-entropy, is pointed out as a necessary feature. The popular dictum “it from bit” does not appear valid unless amended with its obverse “bit from it.”

The HOMO–LUMO molecular orbitals of RbB₈ ^0/− clusters.

Abstract

Alkali metal-doped boron clusters have captured much attention because of their novel electronic properties and structural evolution. In the study of RbB _n ^0/− (n = 2–12) clusters, the minimum global search of the potential energy surface and structure optimization at the level of PBE1PBE by using the CALYPSO method and Gaussian package coupled with DFT calculation; the geometrical structures and electronic properties are systematically investigated. At n = 8, the ground-state structures are composed of an Rb atom above B atoms, forming a structurally stable pagoda cone. By stability analysis and charge transfer calculation, the RbB₈ ⁻ cluster shows more stability. It found that s-p hybridization between Rb atom and B atoms as well as s-p hybridization between B atoms is one of the reasons for the outstanding stability exhibited in the RbB₈ ^0/− clusters by using DOS and HOMO–LUMO orbital contour maps. The chemical bonding of the RbB₈ ^0/− groups was analyzed by using the AdNDP method, and B atoms with larger numbers readily form multi-center chemical bonds with the Rb atom. From the results of the bonding analysis, the interaction between the Rb atom and B atoms strengthens the stability of the RbB₈ ^0/− clusters. It is hoped that this work provides a direction for experimental manipulation.

When a hydrogen atom is confined by a spherical potential well, its ionization due to a static electric field becomes a gradual and reversible phenomenon, that can be studied quantitatively with Quantum Monte Carlo methods.

Abstract

The ionization of the hydrogen atom confined in a spherical potential well and subjected to a static electric field is studied, using the diffusion Monte Carlo (DMC) method. Atomic ionization within a potential well is found to be a stationary, gradual, and reversible process. The value of the electric field at the onset of ionization is of the order of 0.1 atomic units, and depends on the symmetry of the atomic wave function and on the confinement dimension. By decreasing the confinement sphere, the difference between the bound and ionized states disappears, showing that strict confinement leads to pressure ionization of the atom. The off-center case is studied characterizing the potential energy surface (PES), and the transition between field-induced and pressure-induced ionization is confirmed. Except for very weak fields, the minimum of the PES is reached when the proton is in contact with the boundary of the well.

The light passes through the prism at a fixed angle, then couple evanescently though dielectric medium and interact with the silver metal. Surface plasmons are excited at interface of metal and dielectric and decay exponentially along the distance from the interface. Part of the reflected light is absorbed due to coupling of incident light beam with SPPs. The dielectric medium is used to control the sensitivity of SPPs to our chance of demand.

Abstract

In this manuscript, Intensity interrogation of sensitivity of the surface plasmon polariton waves (SPPs) is coherently manipulated, at the interface of four-level dielectric medium and silver metal using prism geometry. Sensitivity of SPPs with respect to refractive index is written as dI/dnd$$ dI/d{n}_d $$. A useful control in sensitivity is reported with probe and control fields detuning, Rabi frequency and decay rate. Sensitivity is a function of probe field detuning and control field Rabi frequency. The maximum sensitivity is reported to 400 Wm−2/RIU$$ 400\;{\mathrm{Wm}}^{-2}/\mathrm{RIU} $$ with probe field detuning and control field Rabi frequency, while minimum sensitivity is investigated to 34 Wm−2/RIU$$ 34\;{\mathrm{Wm}}^{-2}/\mathrm{RIU} $$ with control field phase and control field Rabi frequency. The sensitivity in this manuscript shows useful application in biosensor and photovoltaic devices.

Perylene diimide (PDI) and naphthalene diimides (NDIs) are versatile compounds in supramolecular structures due to absorptive and photoluminescent properties. Synthesized through reflux method, NDI and PDI derivatives were investigated, revealing electron donor/acceptor behavior. Nonlinear optical (NLO) response of ligands, including Gly-PDI, Imi-PDI, L-ala-PDI, and B-ala-PDI, indicated potential for NLO applications. Comprehensive characterization advances understanding of these compounds for charge transfer and nonlinear optical materials.

Abstract

Perylene diimide (PDI) and naphthalene diimides (NDIs) are compounds widely used in supramolecular structures due to their versatile and functional properties. They have high absorptions and photoluminescence capabilities, which make them ideal for electronic transition studies. Reflux method, a widely employed synthetic technique, was utilized to synthesize NDI and PDI derivatives. In this method, the respective amino acids and NTDA (naphthalene-1,4,5,8-tetracarboxylic dianhydride) were combined in acetic acid and the resulting mixture was subjected to reflux. This study centered on a diverse set of NDI and PDI ligands, comprising L-ala-NDI, B-ala-NDI, Gly-NDI, Imi-NDI, Pyr-NDI, L-ala-PDI, B-ala-PDI, Gly-PDI, Imi-PDI, and Pyr-PDI ligands. Crystal structures were obtained for three NDI ligands, while the characterization of all ligands involved several analytical techniques such as NMR, IR, UV, DFT, TD-DFT calculations, and single-crystal x-ray crystallography specifically for the NDI ligands. The investigation focused on studying the electron acceptor/donor behavior of the NDI and PDI ligands, identifying their potential for charge transfer applications. Furthermore, the NLO (nonlinear optical) response of all 10 NDI and PDI ligands was assessed through an analysis involving HOMO-LUMO, TDM, EDDM, NCI, Iso-surface, MEP, natural population, and DOS analysis. This evaluation encompassed the examination of linear polarizability, as well as first and second hyperpolarizability in the context of NLO. The findings of the study revealed that Gly-PDI, Imi-PDI, L-ala-PDI, and B-ala-PDI ligands displayed a higher NLO response compared with the other ligands. These results highlight the potential of these ligands for nonlinear optical applications. The comprehensive characterization and assessment of the NDI and PDI ligands contribute to a deeper understanding of their electron properties, positioning them as promising candidates for charge transfer and nonlinear optical materials.

This work investigates the structural stability, mechanical and thermodynamic properties of two Ti-V solid solutions. It is found that the Ti-V compound prefers to form the V(Ti)_ss solid solution, which remains the cubic structure. Based on the Born stability criteria, the V(Ti)_ss solid solution is a mechanical stability. In particular, the V(Ti)_ss solid solution shows higher volume deformation resistance and better ductility compared to the pure Ti.

Abstract

Although Ti-V based high-temperature alloys are used in aerospace engine, rocket engine and hot sections, the structure and mechanical properties of Ti-V alloys remains controversy. To explore the correlation between structural and mechanical properties, we apply employed the DFT method to study the phases stability, mechanical and thermodynamic properties of Ti-V solid solution. Two Ti-V solid solutions: Ti(V)_ss solid solution and V(Ti)_ss solid solution are discussed. Two Ti-V solid solutions are thermodynamic stability. In particular, the Ti-V solid solution prefers to form V(Ti)_ss solid solution, in while the V(Ti)_ss solid solution remains cubic structure. Furthermore, the Ti(V)_ss solid solution is a mechanical instability. However, the V(Ti)_ss solid solution is a mechanical stability. Here, the bulk modulus, shear modulus and Young's modulus of V(Ti)_ss solid solution are 136.9, 23.5 and 66.7 GPa. In particular, the bulk modulus of V(Ti)_ss solid solution is higher than the bulk modulus of the pure Ti. In addition, the V(Ti)_ss solid solution shows better ductility compared to the pure Ti and V. Naturally, the stability and mechanical properties of V(Ti) solid solution is related to the Ti-V metallic bond because of the localized hybridization between the Ti(3d) and V(3d).

The number of significant figures (SF) of the cusp condition (CC) is approximately half that of the Hartree–Fock total energy (TE). The SFs of expectation values of the other one-electron properties are also smaller than for the TE.

Abstract

The accuracy of the expectation values (<A>$$ <A> $$) of one-electron operators is examined using Hartree–Fock wavefunctions expanded using Λ$$ \Lambda $$ functions. In this expansion, 150 terms, then 149, 148, and 147 terms are used for the s-, p-, d-, and f-symmetries, respectively. The systems investigated are He–Ne and the Group 18 atoms of Ar–Og. The one-electron properties investigated are the cusp condition (CC), the electron density at the nucleus (ρ(0)$$ \rho (0) $$), and <ri>$$ <{r}^i> $$ (i=−2,…,9$$ i=-2,\dots, 9 $$). Convergence of <A>$$ <A> $$ is examined by increasing the number of expansion terms (N$$ N $$) up to the given limit (150). The number of significant figures (SF) of <A>$$ <A> $$ is counted by comparing the calculated value at N$$ N $$=150 (<A(150)>$$ <A(150)> $$) with the extrapolated value <A(∞)>$$ <A\left(\infty \right)> $$. For He, the SF of CC is found to be 26. For the atoms under consideration, the SF of CC is approximately half that of the total energy (TE). The SFs of expectation values of the other properties are also smaller than for the TE.

Mixed cation based hybrid halide perovskite (ABX₃) semiconducting materials have been studied by employing density functional theory formalism. Tolerance and octahedral factors indicate the structural stability of the studied materials. Neagative values of formation energy indicates their thermodynamic stability. Observed band gap values and high optical absorption in the visible range of electromagnetic spectrum manifest their potential to become suitable materials for photovoltaic applications.

Abstract

The development of Pb-free alternatives for perovskite-based photovoltaics is extremely important due to the toxicity of Pb to the environment. Sn-based organic inorganic hybrid halide perovskites are considered to be the most suitable alternative to Pb-based ABX3$$ {}_3 $$ perovskites due to their similar optoelectronic properties. The selection of A site cation in ABX3$$ {}_3 $$ type perovskites is crucial for favorable structural and mechanical properties. Using first principle methods, we have designed and investigated Sn–I based hybrid halide perovskite materials with different organic cations mixed in equal proportions. Observed tolerance (TF) and octahedral factors (μ$$ \mu $$) indicate the formation of stable three-dimensional perovskite structure. Our studied materials also exhibit thermodynamic stability due to the negative value of their formation energies. Observed band gap values indicate the semiconducting nature of our studied perovskite materials. Calculated optical properties indicate that all of the compounds exhibit suitable dielectric functions and absorption coefficients in the visible range of the electromagnetic spectrum. The observed highest value of theoretical power conversion efficiency of MA-AMSnI3$$ {}_3 $$ (11.24%) indicates its potential to be used in photovoltaics. Our investigation will be beneficial for researchers to develop less toxic and efficient perovskite materials for the fabrication of optoelectronic devices.