We have investigated the potential energy curves (PECs) of the LiN heteronuclear diatomic molecule, including its ionic species LiN⁺ and LiN⁻, using explicitly correlated multi-reference configuration interaction (MRCI-F12) calculations in conjunction with the correlation consistent quintuple-𝜁 basis set. The effect of core–valence correlation, scalar relativistic effects, and the size of the basis sets has been investigated. A comprehensive set of spectroscopic constants determined based on the above-mentioned calculations are also reported for the lowest electronic states and all systems, including dissociation energies, harmonic and anharmonic vibrational frequencies, and rotational constants. Additional parameters, such as the dipole moments, equilibrium spin-orbit constants, excitation energies, and rovibrational energy levels, are also documented. We found that the three triplet states of LiN, namely, X ³∑⁻, A ³Π, and 2 ³∑⁻, exhibit substantial potential wells in the PEC diagrams, while the quintet states are repulsive in nature. The ground state of the anion also shows a deep potential well in the vicinity of its equilibrium geometry. In contrast, the ground and excited states of the cation are very loosely bound. Charge transfer properties of each of these states are also analyzed to obtain an in-depth understanding of the interatomic interactions. We found that the core–valence correlation has a substantial effect on the calculated spectroscopic constants.@en

The density functional theory (DFT) framework was used to investigate the intermolecular interactions between cyanogen chloride (CNCl) pollutant gas molecule with pristine boron nitride nanotubes (BNNT), Al-doped boron nitride nanotubes (BNAlNT), and carbon boron nitride nanotubes (BC₂NNT). The geometric structures of the resulting systems have been optimized using different methods, including B3LYP-D3(GD3BJ)/6-311G(d), ωB97XD/6-311G(d), and M06-2X/6-311G(d). The computed adsorption energies suggest that the studied nanotubes can enhance adsorption of CNCl, and thus promote its detection when employed as sensing materials. Wave function analysis has been implemented to study the type of intermolecular interactions at ωB97XD/6-311G(d,p) level of theory. Natural bond orbital (NBO) analysis has been used to study the charge transfer and bond order. Quantum theory of atoms in molecules (QTAIM) analysis has also been used to determine the type of interactions between the target gas and the nanotubes. To investigate the weak intermolecular interactions we also carried out non-covalent interaction analysis (NCI). The results also indicate that the CNCl-nanotube systems are created through physisorption as they are dominated by non-covalent interactions. The predicted adsorption energies increase as follows: BNAlNT: −1.175 eV > BC₂NNT: −0.281 eV > BNNT: −0.256 eV; this shows that the aluminum-doped boron nitride nanotube is the best option from promoting adsorption of the target gas among them. The HOMO–LUMO energy gaps were as follows: BNNT: 7.090, BNAlNT: 9.193, and BC₂NNT: 7.027 eV at B3LYP-D3/6-311G(d) level of theory.

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The ability of carbon- and silicon-based nanotubes, including pure carbon, silicon carbide, and Ge-doped silicon carbide nanotubes (CNT, SiCNT, SiCGeNT, respectively), for sensing highly toxic dichlorosilane (H2SiCl2) are investigated using quantum chemistry calculations. The intermolecular interactions between the sensing material and the gas molecule have been investigated with the density functional theory calculations with a functional that includes dispersion terms. The selected method employed is B3LYP-D3 (GD3BJ)/6-311G(d), while other functionals including PBE0, ωB97XD, and M06-2X have been used for comparison. The quantum theory of atoms in molecules (QTAIM) analysis is employed to check the type of intermolecular interactions. Natural bond orbital (NBO) calculations have been used to deduce the bond orders. The findings of this work indicate that the adsorption of the H2SiCl2 is a physisorption process, which is very desirable for its function as a sensing element. The Ge-doped nanotube offers maximum adsorption energy in comparison to CNT and SiCNT.@en

In this paper, we have theoretically determined the possibility of adsorption of the gaseous CH₂N₂ molecule on the surface of X₁₂Y₁₂ nanocages, where X = B, Al, Ga and Y = N, P, As. The electronic structure calculations have been performed by density functional theory (DFT) using four functionals (i.e., B3LYP-D3, M06-2X, ωB97XD, and CAM-B3LYP), together with the 6-311G(d) basis function. We find that the adsorption of CH₂N₂ on top of the X–Y bond of the nanocage is the most preferred site for adsorption. The adsorption process is accompanied by a charge-transfer phenomenon, which results in a strong bond between the terminal N atom of diazomethane and the X atom of the nanocage. This gives rise to significant changes in the highest and lowest occupied molecular orbital (HOMO and LUMO, respectively) energies and thus attribute properties to the nanocages that enable themto act as building blocks of CH₂N₂ sensing materials.

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We have investigated the possibility of utilizing various single-walled pristine and doped carbon nanotubes as adsorbents for the 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124) gaseous molecule. Three candidates, including pristine carbon nanotube (CNT), silicon carbide nanotube (SiCNT) and germanium-doped SiCNT (SiCGeNT) are identified and evaluated theoretically. The quantum simulations have been performed at the density functional theory (DFT) level with four different functionals (i.e., M06-2X, ωB97XD, CAM-B3LYP and B3LYP-D3) with a split-valence triple-zeta basis set (6-311G(d)). We found that adsorption on the SiCGeNT is most favourable, while that on the pristine CNT yields the lowest adsorption energy. Adsorption on these nanotubes is not accompanied by an active charge-transfer phenomenon; instead, it is driven by weak van der Waals forces. The HOMO–LUMO energy gaps drastically change when the dopant atom is added to the SiCNT, thereby improving their overall adsorption capability. Among all of the adsorbents investigated here, SiCGeNT shows the most favourable for designing effective HCFC-124 nanosensors.

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There is a compelling reason to design cost-effective sensors to detect and measure harmful molecules such as dichlorosilane (H₂SiCl₂) in the air. In this work, density functional theory (DFT) has been used to study the nature of the intermolecular interactions between the H₂SiCl₂ gas molecule with a single-walled pristine, Al-doped, and Ga-doped boron nitride nanotubes (BNNT, BNAlNT, and BNGaNT, respectively) to investigate their potential in gas-sensing applications. Full-dimensional geometry optimization and adsorption energies were calculated with four functionals: PBE0, M06-2X, ωB97XD, and B3LYP-D3 with a 6-311G(d) basis set. We find that the B, Al, or Ga atoms provide the most favorable sites for adsorption of the H₂SiCl₂ molecule. The adsorbate is more tightly bound to the surface of the doped rather than of the pristine BNNT nanotubes, demonstrating a larger energy gain due to adsorption. This is due to the fact that H₂SiCl₂ interacts with pristine BNNT through weak Van der Waals forces but seemingly has stronger ionic interactions with the doped variants. In general, introducing impurities can improve the selectivity and reactivity of the BNNT toward H₂SiCl₂. Among all of the absorbents, we find that BNGaNT exhibits the highest affinity toward H₂SiCl₂, and therefore holds a higher potential compared to the rest of the nanotubes investigated here for designing materials for dichlorosilane sensors.

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The feasibility of detecting diazomethane (CH₂N₂) in the gas phase by adsorption onto the exterior surface of inorganic-based X₁₂O₁₂ (where X can be Be, Mg, or Ca) nanocages is investigated here using DFT. All the structures, including those of the pristine CH₂N₂ and of the nanocages, as well as of the CH₂N₂/nanocage systems, have been optimized using the B3LYP-D3, M06-2X, ωB97XD, and CAM-B3LYP functionals, in conjunction with 6-311G(d) basis set. NBO, NCI, and QTAIM analyses results are in good agreement with each other. Furthermore, the Density Of States (DOSs), the natural charges, the Wiberg Bond Indices (WBI), and natural electron configurations were considered to investigate the nature of intermolecular interactions. The energy calculations indicate a strong size-dependent adsorption, with the nanocages comprised of large atoms being able to attract CH₂N₂ more strongly, and hence bind with it more effectively. The adsorption incurs also significant changes to HOMO and LUMO energies.

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