الفهرس 
Definition of Computational ChemistryOnly 14 pages are availabe for public view
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Abstract
Summary and conclusion
This thesis presents a computational study for the sensitivity of some toxic gases at solid surfaces. Density functional theory (DFT) calculations have been carried out using Gaussian 09 code to examine: (i) DFT study of adsorbing SO2, NO2, and NH3 gases based on pristine and carbon doped Al24N24 nanocages. (ii) SF6 decomposed products based on AlN nanocage. (iii) The adsorption of SO2, SCO, H2S, CS2, HCHO, and CH4 on C24N24 nanocages and Li/Na-doped C24N24.
The computational work was completed with resources provided by the CompChem Lab (Minia University, Egypt, http://hpc.compchem.net/)
The thesis consists of three chapters scheduled as follow:
Chapter 1
This chapter presents a literature survey and a review of theory:
Density functional theory (DFT) as well as the methods and simulation techniques employed in the calculations.
Chapter 2
This chapter is divided into two parts:
In Part1, the aim was to investigate the use of Al24N24 and Al24N23C nanocages toward three harmful gases (NO2, SO2, and NH3). The adsorption properties were determined through adsorption energies, charge transfer, dipole moment, thermodynamic parameters, PDOS, NCI, and QTAIM, and the following results are obtained:
1. Introducing carbon doped increases the adsorption energies for NO2 and SO2 gases, while decreasing for NH3 gas.
2. The charge is transferred from the NH3 gas molecule to the nanocage, while for NO2 and SO2 systems, the charge transfers from the nanocage to the SO2 and NO2 gas molecules except configurations C1 and D1.
3. The directions of dipole moment vectors for the NH3 system point forward to this group, while dipole moment vectors of the SO2 and NO2 adsorbed on Al24N24 and Al24N23C nanocages point away from these two groups except configuration D1.
4. The Gibbs free energy change (ΔG) for all configurations are negative except A1 and G2 have a positive value confirming weak adsorption for these complexes.
5. The energy gaps decreased after adsorping NO2, SO2, and NH3 on Al24N24 and Al24N23C nanocages.
6. Higher interaction intensity was observed for C2 and E2 configurations due to the partial covalent contact between the SO2, and NO2 molecules with the Al24N23C nanocage.
7. The results obtained from QTAIM for the C2 complex indicate that the N-C bond should be regarded as a strong polar covalent bond because its ρr value is 0.326 a.u and a weaker association between NH3 and Al24N24 nanocages is indicated by electron density (0.050 a.u.) that is lower than that of configuration C2 and E2.
These results confirm that Al24N24 and Al24N23C nanocages may be used as promising materials for the removal of NO2, SO2, and NH3 toxic gases.
In part 2, investigate the Al24N24 nanocage as a sensing material for SF6 decomposed products (SO2, SOF2, and SO2F2) using the density functional theory (DFT). The structural parameters of these gases on the nanocage were determined such as adsorption energy, frontier orbitals, charge transfer using NBO, and density of states. The results reveals that the adsorption of SO2 and SOF2 gases are chemisorption on the Al24N24 nanocage, while SO2F2 gas is physisorbed on the nanocage which can be desorbed easily.
Chapter 3
This chapter investigates the adsorption properties of Li/Na doped C24N24 nanocages and their interaction with various toxic gas molecules. Results indicate that the introduction of Li/Na atoms enhances the adsorption of gas molecules due to increased binding energies and altered electronic properties. Specifically, the adsorption of SO2, SCO, H2S, CS2, HCHO, and CH4 on Li/Na doped C24N24 demonstrates varied interaction strengths compared to pristine C24N24. Moreover, the decorated nanocages exhibit altered electronic structures, evidenced by changes in energy gaps and charge transfer upon gas adsorption. Frontier molecular orbital analysis suggests improved reactivity and electrical conductivity of the complexes, making them potentially suitable for gas sensing applications. However, the recovery times indicate limitations in sensing abilities for certain gas molecules. Furthermore, conceptual DFT analysis highlights changes in ionization potential, electron affinity, and electrophilicity upon gas adsorption and Li/Na decoration, underscoring the influence of metal doping on the chemical properties of C24N24 nanocages. Thermodynamic parameters suggest that the adsorption processes are generally nonspontaneous, with the presence of Li/Na atoms favoring select configurations. Overall, the findings provide valuable insights into the design and application of metal-doped C24N24 nanocages for gas sensing and catalytic purposes.