Cn,CnH and their anions: Quest for linearity with n≤8 even versus odd,and beyond

Using the concept of quasi-molecule (“tile”) and the database of quasi-molecules embedded on a parent molecule, it is discussed whether the latter can attain linear form or otherwise. Besides anew accurate optimization of all tiles (quasi-triatomics) at various levels of ab initio theory and basis-sets, the nature of the predicted stationary points for the title parent molecules is probed through a priori calculations here too reported. Also discussed is the common rule that even- $n$ ${\text{C}}_n{\text{H}}^{-}$ anions are linear while odd-numbered ones tend to have nonlinear isomers. The reported quasi-molecule approach is general, and allow the prediction of linearity or otherwise of the parent systems prior to calculations on them. When based on an extension of the bisection method (Varandas, Int. J. Quantum Chem. 2023 , 123, e27036.), it is easy to use even for large parent molecules, as illustrated for neutral and anionic carbon clusters with $n\ge 9$.     

Topological defects on the energy spectra of diatomic molecules embedded with shifted Deng–Fan oscillator potential under AB flux field

A study on the effect of point like global monopole topological defects on the energy eigenvalues of the diatomic molecules $H_2$, $LiH$, $CO$, $HCl$ embedded with Shifted Deng–Fan Oscillator Potential under the influence of Aharonov–Bohm flux field has been made here. Asymptotic Iteration Method (AIM) is used to find out the bound state solutions for arbitrary $l$ states by solving the non-relativistic Schrödinger equation. A Pekeris-type approximation has been used to approximate the centrifugal barrier term. It is observed that, energy levels of the diatomic molecules is significantly affected by the global effects of the point like global monopole, flux field and effective potential field.     

Modeling of a linear ion trap with driving rectangular waveforms

We consider the operation of a digital linear ion trap with resonant radial ejection. A sequence of rectangular voltage pulses with a dipole resonance signal is applied to the trap electrodes. The periodic waveform is piecewise constant, has zero mean, and is determined by an asymmetry parameter $d$: one value is taken on interval $\left(0,\mathit{dT}\right)$ and another on $\left(\mathit{dT},T\right)$, where $T$ is the RF period. Ion mass scanning is performed by varying the asymmetry parameter $d$ and amplitude of the negative pulse part with time. The ion oscillation frequencies and acceptance of the linear trap are calculated. The dependence of the ion mass to charge ratio $m/z$ on the parameter $d$ is $m/z~d^2$. The maximum value is about $m/z=30$ kDa for typical parameters of the linear trap: frequency 0.5 MHz, rod radius 4 mm, and negative pulse amplitude 1 kV. The dipolar excitation frequency is 0.125 MHz at which the LIT acceptance is maximal.     

A DFT calculation of electronic structures,magnetic, and thermoelectric properties of the new equiatomic quaternary Heusler alloy RuTiCrSi

The stabilities, mechanical, electronic, and magnetic properties of the new equiatomic quaternary Heusler alloy (EQHA) RuTiCrSi were investigated using the Kohn-Sham DFT (KS-DFT) calculations within the generalized gradient approach (GGA), the modified version of the exchange potential introduced by Becke and Johnson in addition to the GGA (mBJ-GGA), and Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional. The ground-state equilibrium energy reveals that the ferromagnetic with type 2 structure is the more stable. The RuTiCrSi is energetically, mechanically, and dynamically stable. The calculated self-consistent total magnetic moment is 2 μB and agrees well with the Slater-Pauling rule of $M_{\mathrm{t}}=\left|Z_{\mathrm{t}}-24\right|$. The electronic structure results from mBJ-GGA and HSE06 functionals show a half-metallic behavior. A high Curie temperature is obtained using the mean-field approximation. The thermoelectric response was calculated using the semi-classical Boltzmann transport equation under constant relaxation time. The maximum value of Seebeck coefficient is observed at the ambient temperature of $741\mathrm{\mu V}{\mathrm{K}}^{-1}$. It was also observed that the power factor increases significantly as temperature rises. Therefore, the new EQHA RuTiCrSi seems to be a potential candidate for spintronic thermoelectric applications.     

The confined helium atom: An information–theoretic approach

In this article, we study the helium atom confined in a spherical impenetrable cavity by using informational measures. We use the Ritz variational method to obtain the energies and wave functions of the confined helium atom as a function of the cavity radius $r_0$. As trial wave functions we use one uncorrelated function and five explicitly correlated basis sets in Hylleraas coordinates with different degrees of electronic correlation. We computed the Shannon entropy, Fisher information, Kullback–Leibler entropy, Tsallis entropy, disequilibrium and Fisher–Shannon complexity, as a function of $r_0$. We found that these entropic measures are sensitive to electronic correlation and can be used to measure it. As expected these entropic measures are less sensitive to electron correlation in the strong confinement regime ( a.u.).     

On physical analysis of entropy measures for sodium oxide via statistical models

This study delves into a comprehensive physical analysis of entropy measures applied to sodium oxide ${\text{Na}}_2\text{O}$. A key idea in information theory and thermodynamics, entropy is essential to comprehending the stability of a system. The study clarifies the intricate relationships and physical properties of ${\text{Na}}_2\text{O}$ by combining theoretical analysis with statistical methods, providing important knowledge for material design and industrial operations. In a chemical graph, atoms are shown by vertices while their bonding are illustrated by edges. Sodium oxide is a major contributor to manufacture glass, it also has potential applications in ${\text{CO}}_2$ sequestration, transparent materials, biomedical devices and nano grating glass. A topological index is a relationship between the molecular graph and its topology. We have computed various graph entropies based on different topological indices of chemical graph of sodium oxide. Further we have integrated these graph entropies with distinct thermodynamical measures of sodium oxide by developing mathematical models between both quantities. We have developed these mathematical frameworks in MATLAB. All the models are selected relying on the least mean squared error or sum of squared error.     

Physical versus non-physical effective nuclear masses for non-adiabatic corrections to molecular spectra

Two types of developments for very accurate non-adiabatic corrections to rovibrational molecular energy levels, one of a formal nature and the other of a heuristic nature, lead to fundamentally different approaches for effective nuclear masses. The former yields effective masses that have non-physical interpretation at some ranges of nuclear distances. The later uses physical masses obtained from electronic structure calculations. This paper contains a brief review of the subject and proposes procedures to improve and generalize the heuristic approach. Comparisons are made of the results obtained by the two approaches for the H ${}_2$ molecule, since no further calculations were found with the proper accuracy, but some issues involving the HeH ${}^{+}$ ion and the water molecule are discussed. The conclusion is that the heuristic approach has many advantages over the formal one, namely, equivalent accuracy and physically grounded qualitative interpretation. But, moreover, it seems to be presently the only method that allows non-adiabatic calculations for well isolated states of larger molecules.     

Effect of thermal fluctuations on the electronic excitation energies of linear polyenes: A combined molecular dynamics and TD-DFT study

In the present study, thermally averaged electronic excitation energies (the so-called dynamic approach) are quantitatively assessed for a model molecular system composed of a series of increasingly longer chains of simple linear polyenes. The molecular dynamics trajectories are calculated using the semi-empirical “Geometry, Frequency, Noncovalent, eXtended Tight Binding” (GFN2-xTB) method, while TD-DFT vertical excitation energies of selected snapshots are obtained with the spin-component-scaled double hybrid density functional SCS-wPBEPP86. Boltzmann weighted average excitation energies were then calculated in order to take into account the contribution of thermal motions. Excitation energies via the dynamic approach are compared with that of the static approach in which thermal fluctuations are not considered. The differences between the dynamic and the static approaches were found to be around the range $-0.01$ to $+0.01$ eV for polyenes up to 44 carbon atoms. This range of errors is relatively small in comparison with typical errors produced by using different density functionals and/or basis sets. Therefore, the electronic excited states of small to medium lengths of linear polyenes (less than 50 carbon atoms) can be safely modeled via the static approach. However, extrapolation of the results to longer polyenes indicates that the difference between both approaches is estimated to be 0.05 eV for polyenes containing 100 carbon atoms, which suggests that considering thermal motions in the calculations of excitation energies is recommended for such long conjugated molecular systems.     

Hybrid Membrane of Agarose and Lanthanide Coordination Polymer: a Selective and Sensitive Fe3+ Sensor

A new hybrid membrane was prepared by a facile method based on a highly luminescent lanthanide coordination polymer and agarose. The soft membrane was characterized by FT‐IR, PXRD, SEM and luminescence. It is found that the soft membrane is a highly selective and sensitive sensor, among 19 metal ion solutions of Fe³⁺, Mg²⁺, Li⁺, Ca²⁺, Zn²⁺, Cu²⁺, Ba²⁺, Mn²⁺, Ru³⁺, Cr³⁺, Ag⁺, Sr²⁺, Cd²⁺, Na⁺, Ni²⁺, Pb²⁺, Fe²⁺, Hg²⁺ and Ca²⁺, only Fe³⁺ quench the luminescence. The sensing results can be distinguished by the naked eye in daylight or by irradiation of a portable UV light at the scene. Mechanism studies reveal the sensing is due to the decomposition of the coordination polymer 1 which induced by slow permeation of Fe³⁺. Further studies found anions of ${\mathbf{BO}}_{\mathbf{3}}^{?}$, ${\mathbf{CO}}_{\mathbf{3}}^{\mathbf{2}?}$, ${\mathbf{H}}_{\mathbf{2}}{\mathbf{PO}}_{\mathbf{4}}^{?}$, Br^?, Cl^?, ${\mathbf{ClO}}_{\mathbf{4}}^{?}$, ${\mathbf{H}}_{\mathbf{2}}{\mathbf{PO}}_{\mathbf{4}}^{?}$, I^?, ${\mathbf{IO}}_{\mathbf{3}}^{?}$ and ${\mathbf{NO}}_{\mathbf{3}}^{?}$ will not quench the luminescence of the hybrid membrane, which imply that other anions in water would not disturb the detection result.     

Spherically confined hydrogenic atoms under classical non-ideal plasmas: Scaling law for the critical cage size

An elegant calculation is carried out to investigate the effects of the non-ideality of classical plasma on the energy levels of the hydrogenic atoms held in a spherical cage. Organized effect of the non-ideal classical plasma is described by an analytical pseudopotential which contains the Debye length $D$ and non-ideality parameter $\gamma$ as parameters. Convergent results for the bound states are obtained variationally by utilizing a large trail function containing cosine term which automatically takes care of the requisite boundary conditions. For the plasma-free case, our results are in excellent agreement with the most accurate results available in the literature. An inclusive study is made to explore the changes emerging in the energy levels due to the variation of the plasma parameters and cage size. Special emphasis is made on the determination of critical cage size precisely. The present study specifically reveals that the increasing plasma non-ideality leads to the elongation of the critical cage size. Moreover, it is empirically found that the critical cage size for a given hydrogenic atom can be obtained from a scaling law.     

The role of monomer geometry on the properties of polyolefins: A numerical study

We explore the role of monomer geometry on the structural, dynamic, and thermodynamic properties of polyolefis by employing all-atom molecular dynamic simulations. Specifically, we compare properties of atactic polyolefins in the molten state including polypropylene (aPP), a short-chain branched polymer: poy(1-hexene) (aPH), and a polymer having cyclic olefins: poly(vinyl cyclobutane) (aPVCB). We find polymers having the same chain mass and atom composition (hydrocarbon-based molecules), but having different monomer architecture differ strongly in material properties. In particular, the polymer glass transition ( $T_{\mathrm{g}}$) and bulk modulus ( $B$) show higher values for aPVCB in comparison to aPP and aPH. This increase is caused by having the carbon atoms in a cyclic structure, making aPVCB achieve higher mass and energy densities. By contrast, adding linear short side chains to polymer backbones causes a reduction in $T_{\mathrm{g}}$ and $B$, since side chains make backbones displace each other reducing their packing and thus their mass and energy densities. More broadly, our numerical results suggest that the incorporation of VCB monomers to linear polyolefins will enhance their properties, opening the possibility for designing a new set of materials.     

Synthesis and characterization of the azido-bound five-coordinate high-spin iron(II) “picket fence” porphyrin complex

An Fe(II)-azido five-coordinate picket fence porphyrin complex with the formula [Na(2,2,2-crypt)][Fe^II(TpivPP)(N₃)] · 3C₆H₅Cl (TpivPP = α,α,α,α-tetrakis(o-pivalamidophenyl)porphinato, known as a picket fence porphyrin, and 2,2,2-crypt is the cryptand-222) has been synthesized and characterized. The synthesis utilizes cryptand-222 to solubilize sodium azide in the preparation procedure. The UV–Vis and IR spectroscopic data are consistent with an azido ferrous porphyrinate. The X-ray structural analysis and the Mössbauer results indicate that the ion complex [Fe^II(TpivPP)(N₃)]⁻ is high-spin and has the (d_xy)²(d_xz)¹(d_yz)¹(d_z2)¹(d_x2-y2)¹$({\text{d}}_{\mathit{xy}}{)}^2({\text{d}}_{\mathit{xz}}{)}^1({\text{d}}_{\mathit{yz}}{)}^1({\text{d}}_{z^2}{)}^1({\text{d}}_{x^2-y^2}{)}^1$ ground state electronic configuration.     

Comparative analysis of modified reverse degree topological indices for certain carbon nanosheets using entropy measures and multi criteria decision-making analysis

The diverse applications of various carbon nanostructures have sparked significant research interest. The potential significance of carbon nanosheets lies in their exceptional mechanical, electrical, and thermal properties, enabling advancements in various technological applications such as energy storage, electronics, and engineering, playing important roles in material science and nanotechnology. In the field of mathematical chemistry, topological indices play a crucial role by providing numerical insights into molecular structures. These insights facilitate predictive correlations with chemical properties and reactivity, ultimately finding utility in areas like drug design and material sciences. Expanding on this, the study delves into the application of entropy-based methodologies that originates from the arrangement of chemical structures. By assessing the complexity and other features of these structures, graph entropies are translated into information-theoretic metrics. This article examines modified reverse degree-based topological indices with its universal applicability to all degree-based indices. The standout feature is the adaptable parameter “ $k$” effectively shaping the molecular graphs degree sequence to best fit each dataset with their unique physicochemical properties, distinguishing it from conventional fixed degree methodologies. Additionally, we investigate graph entropies and examine the impact of varying the parameter “ $k$” on entropy measures across a range of nanosheet structures. The research focuses on characterizing carbon nanosheets, employing effective (MCDM) multiple criteria decision-making methods like VIKOR, TOPSIS, and SAW. Through these techniques, a comprehensive comparative analysis of the nanosheets is conducted with the aim of establishing optimized rankings for each type based on their unique attributes and characteristics.     

Compressed lithium atom under Debye screening

In the present paper, we introduced two approximation methods to investigate the spherically compressed lithium atom under the influence of Debye plasma. Specifically, the diffusion and the variational Monte Carlo methods are used for the first time to study this case. We incorporated an exponential screening into the nuclear Coulomb potential to account for the plasma influence. We focused our investigation on analyzing the combined effect of compression and plasma environment on the behavior of the lithium atom in its ground state. The resulting outcomes exhibited consistent pattern across various confinement radii $R_c$ and Debye plasma lengths $\mu$. Many of the results are novel contributions, as they have yet to be explored. Moreover, the findings from this study demonstrated reasonable agreement with the limited existing theoretical results.