حيدر عبدالرزاق عبدالحسين المدني

Developing effective methods and materials for hydrogen (H2) storage in hydrogen fuel cell vehicles is essential to reduce reliance on fossil fuels in the transportation sector. Carbon-based materials have been proposed as promising candidates for H2 storage. In this article, van der Waals-corrected density functional theory calculations are employed to explore the potential of ψ-graphene monolayers doped with transition metals (Sc, Ti, and V) as promising H2 storage materials. Metal dopants strongly bind with ψ-graphene with binding energies of 4.38, 4.11, and 2.44 eV for Sc, Ti, and V, respectively. Additionally, the diffusion energy barriers of (0.5, 0.51, and 0.24 eV) for Sc, Ti, and V, respectively, on the ψ-graphene surface significantly reduce the calculated metal agglomeration probability when Sc, Ti, and V are displaced from the Hp site to the Ha site. Metal decorated ψ-graphene can bind up to six H2 molecules, with average adsorption energies of 0.31, 0.37, and 0.41 eV per H2 molecule for Sc, Ti, and V, respectively. The calculated H2 storage capacities are 5.97%, 5.89%, and 5.80% for decorated ψ-graphene systems with Sc, Ti, and V, respectively. These calculated properties align well with the U.S. Department of Energy's criteria for reversible H2 storage in fuel cell vehicles. Thermodynamic analysis indicates that Sc@ψ-graphene and Ti@ψ-graphene offer the most favorable hydrogen storage performance under realistic operating conditions (30 atm and 25 °C for adsorption; 3 atm and 100 °C for desorption). AIMD simulations conducted at 400 K demonstrate the excellent thermal stability of X@ψ-graphene (X = Sc, Ti, V) complexes, even at elevated doping concentrations. Throughout the 5 ps simulation, regulated by a Nosé–Hoover thermostat, the systems preserved their structural integrity, highlighting their resilience to thermal fluctuations and suitability for high-temperature applications. Consequently, ψ-graphene doped with Sc, Ti, or V emerges as an exceptional material for reversible H2 storage.

Amide bonds are ubiquitous and valuable motifs in synthetic chemistry, found in a wide range of applications such as the backbone of proteins and pharmaceutical agents. Thus, environmentally friendly and selective methods for synthesizing amide bonds are important. Herein, we report a simple, efficient, and rapid route to access a range of functionalized amides from non-activated carboxylic acids and amines using indium (III) trifluoromethanesulfonate as an efficient catalyst. A wide range of carboxylic acids – including aliphatic, aromatic, heterocyclic, and dicarbonyl acids – participate smoothly in these reactions, generating structurally diverse amides in moderate to good yields (up to 91 % in 24 examples). The reactions are conducted in dry tetrahydrofuran (THF) under reflux conditions. Furthermore, this amidation strategy provides a method for addressing challenging molecules, such as protected amino acids, to produce biocompatible products. These products can then be used as substrates for various organic transformations, including C−H functionalization reactions. We also demonstrate the synthetic utility of our protocol through the synthesis of essential substrates in organic and medicinal chemistry by reacting N-protected carboxylic acids with 8-aminoquinoline to produce a series of biologically valuable compounds. Five of these products, named 4 f, 4p, 9a, 9c, and 9d, have been biologically evaluated through an in-silico study. The interaction of these compounds with receptor protein 8DQT was examined to assess their potential as drug candidates for hypertension treatment. Effective binding was detected between these compounds and the receptor. Data from molecular docking studies show that compounds 4d and 4 m are the most active, with binding scores of −8.8 and −8.6 kcal/mol, respectively. However, compound 4 m exhibited a stronger binding affinity than compound 4d over the course of dynamic simulation. Our ADMET study suggests that all five compounds are highly safe in the body. Based on the BOILED-Egg model study, good absorption is suggested for all the molecules, and they can cross the blood-brain barrier.

Toxic gases such as NO, CO, and SO can cause severe environmental problems. Therefore, research efforts on designing sensors for these gases are imperative. In this study, we have used first-principles calculations to unveil the atomic configurations, adsorption properties, electronic structures, and optical characteristics of these poisonous gases on Ga-doped AlN monolayer nanosheets from a physical perspective. Our findings reveal that the configurations, band structure, adsorption energy, and sensitivity of the nanosheets are significantly affected by the dopant (Ga atom). A physosorption is suggested for CO and NO adsoption system while a chemisorption is characterised for SO system on the Ga-site, indicating their potential as filtration and sensing materials for NO, CO, and SO gases. NO and CO systems are found to show similar optical properties, with absorption peaks in the ultraviolet (UV) region. The refractive index values for NO and CO adsorbants are 1.3 and 3.56 for SO adsorbant on Ga-site, with a slight increase in the visible area. These insights can aid in developing new AlN monolayer-based materials for environmental and sustainability applications.

The limited mutual solubility between Au and Fe in the bulk scale has inhibited the formation of their alloys. Here we report the lowest energy structures of AuFe alloys in subnanometre scale, employing the Mexican Enhanced Genetic Algorithm coupled with density functional theory. The energetics, structural transitions, and tendency of segregation have been analysed by different stability criteria. Physico-chemical properties for all compositions have been studied using Koopman’s approximation. The topological parameters for the metal-metal interactions have been calculated using QTAIM theory. Exploring such valuable theoretical insights is of great importance in investigating new AuFe nanoalloy-based materials for technological applications.

The Mexican enhanced genetic algorithm has been used to study the structural and energetic properties of Pd, Ni, and Ni–Pd nanocluster structures with 3–10 atoms. Density functional theory (DFT) calculations have been performed to investigate the structural behavior, spin magnetic moment, and stability as a function of cluster size and composition. Various stability criteria (for example, binding energies, second differences in energy, and mixing/excess energies) have been used to evaluate the energetics, structure, and tendency to segregation in sub-nanometer Ni–Pd clusters. The ability of the approach in searching for global minima (i.e., the lowest-energy isomers) has been assessed using a systematic homotop search of monosubstituted clusters and the preferred doping sites.

The introduction of dopant atoms into metal nanoparticles is an effective way to control the interaction with adsorbate molecules and is important in many catalytic processes. In this work, experimental and theoretical evidence of the influence of Pd doping on the bonding between small cationic AuN+ clusters and CO is presented. The CO adsorption is studied by combining low-pressure collision cell reactivity and infrared multiple photon dissociation spectroscopy experiments with density functional theory calculations. Measured dissociation rates of cluster–CO complexes (N ≤ 21) allow the estimation of cluster–CO binding energies, showing that Pd doping increases the CO adsorption energy to an extent that is size-dependent. These trends are reproduced by theoretical calculations up to N = 13. In agreement with theory, measurements of the C–O vibrational frequency suggest that for the doped PdAuN−1+ (N = 3–5, 11) clusters, CO adsorbs on an Au atom, while for N = 6–10 and N = 12–14, CO interacts directly with the Pd dopant. A pronounced red-shifting of the C–O vibrational frequency is observed when CO interacts directly with the Pd dopant, indicating a significant back-donation of electron charge from Pd to CO. In contrast, the blue-shifted frequencies, observed when CO interacts with an Au atom, indicate that σ-donation dominates the Au–CO interaction. Studying such systems at the sub-nanometre scale enables a fundamental comprehension of the interactions between adsorbates, dopants and the host (Au) species at the atomic level.

Catalysis by AuCu nanoclusters is a promising scientific field. However, our fundamental understanding of the underlying mechanisms of mixing in AuCu clusters at the sub-nanometre scale and their physico-chemical properties in both the gas-phase and on oxide supports is limited.We have identified the global minima of gas-phase and MgO(100)-supported AuCu clusters with 3–10 atoms using the Mexican Enhanced Genetic Algorithm coupled with density functional theory. Au and Cu adatoms and supported dimers have been also simulated at the same level of theory. The most stable composition, as calculated from mixing and binding energies, is obtained when the Cu proportion is close to 50%. The structures of the most stable free AuCu clusters exhibit Cu-core/Au-shell segregation. On theMgO surface however, there is a preference for Cu atoms to lie at the clustersubstrate interface. Due to the interplay between the number of interfacial Cu atoms and surface-induced cluster rearrangement, on the MgO surface 3D structures become more stable than 2D structures. The O-site ofMgO surface is found to be the most favourable adsorption site for both metals. All dimers favour vertical (V) configurations on the surface and their adsorption energies are in the order: AuCu < CuCu < AuAu < AuCu (where the underlined atom is bound to the Osite). For both adatoms and AuCu dimers, adsorption via Cu is more favourable than Au-adsorbed configurations, but, this disagrees with the ordering for the pure dimers due to a combination of electron transfer and the metal-on-top effect. Binding energy (and second difference) and HOMO-LUMO gap calculations show that even-atom (even-electron) clusters are more stable than the neighbouring odd-atom (odd- electron) clusters, which is expected for closed- and open-shell systems. Supporting AuCu clusters on the MgO(100) surface decreases the charge transfer between Au and Cu atoms calculated in free clusters. The results of this study may serve as a foundation for designing better AuCu catalysts.

We analyze in detail how the interplay between electronic structure and cluster geometry determines the stability and the fragmentation channels of single Pd doped cationic Au clusters, PdAuN-1+ (N=2−20). For this purpuse, a combination of photofragmentation experiments and density functional theory calculations was employed. A remarkable agreement between the experiment and the calculations is obtained. Pd doping is found to modify the structure of the Au clusters, in particular altering the 2D to 3D transition size, with direct consequences on the stability of the clusters. Analysis of the electronic density of states of the clusters show that, depending on cluster size, Pd delocalizes one 4d electron, giving an enhanced stability to PdAu6+, or remains with all 4d10 electrons localized, closing an electronic shell in PdAu9+. Furthermore, it is observed that for most clusters, Au evaporation is the lowest-energy decay channel, although for some sizes Pd evaporation competes. In particular, PdAu7+ and PdAu9+ decay by Pd evaporation due to the high stability of the Au7+ and Au9+ fragmentation products.

To contribute to the discussion of the high activity and reactivity of Au–Pd system, we have adopted the BPGA-DFT approach to study the structural and energetic properties of medium-sized Au–Pd sub-nanometre clusters with 11–18 atoms. We have examined the structural behaviour and stability as a function of cluster size and composition. The study suggests 2D–3D crossover points for pure Au clusters at 14 and 16 atoms, whereas pure Pd clusters are all found to be 3D. For Au–Pd nanoalloys, the role of cluster size and the influence of doping were found to be extensive and non-monotonic in altering cluster structures. Various stability criteria (e.g. binding energies, second differences in energy, and mixing energies) are used to evaluate the energetics, structures, and tendency of segregation in sub-nanometre Au–Pd clusters. HOMO–LUMO gaps were calculated to give additional information on cluster stability and a systematic homotop search was used to evaluate the energies of the generated global minima of mono-substituted clusters and the preferred doping sites, as well as confirming the validity of the BPGA-DFT approach.

Over the past two decades, there have been significant developments of sophisticated search algorithms, in particular, genetic algorithms (GAs). GAs have been used to predict the structures (and hence the physical and chemical properties) of mixed-metal “nanoalloy” clusters, with an emphasis on subnanometer clusters, via the coupling of the GA with electronic structure calculations, particularly density functional theory. In collaboration with a number of theoreticians and experimentalists, we have employed different computational approaches and high-performance computing architectures to develop our in-house GA codes and used them to complement experimental studies. In this chapter, we review the basics of GAs, as applied to clusters, and historical developments of the GA programs to allow the exploration of cluster energy surfaces and the search for global minima, at different levels of theory. A range of example applications are introduced, included optical, electronic, and catalytic applications of free and surface-supported pure metal clusters and nanoalloys. Finally, we discuss some possible future developments.

The structures and surface adsorption sites of Pd–Ir nanoalloys are crucial to the understanding of their catalytic performance because they can affect the activity and selectivity of nanocatalysts. In this article, density functional theory (DFT) calculations are performed on bare Pd–Ir nanoalloys to systematically explore their stability and chemical ordering properties, before studying the adsorption of CO on the nanoalloys. First, the structural stability of 38-atom and 79-atom truncated octahedral (TO) Pd–Ir nanoalloys are investigated. Then the adsorption properties and preferred adsorption sites of CO on 38-atom Pd–Ir nanoalloys are considered. The PdshellIrcore structure, which has the lowest energy of all the considered isomers, exhibits the highest structural stability, while the PdcoreIrshell configuration is the least stable. In addition, the adsorption strength of CO on Ir atoms is found to be greater than on Pd for Pd–Ir nanoclusters. The preferred adsorption sites of CO on pure Pd and Ir clusters are in agreement with calculations and experiments on extended Pd and Ir surfaces. In addition, d-band center and charge effects on CO adsorption strength on Pd–Ir nanoalloys are analyzed by comparison with pure clusters. The study provides a valuable theoretical insight into catalytically active Pd–Ir nanoalloys.

The global optimization of subnanometer Ru–Pt binary nanoalloys in the size range 2–8 atoms is systematically investigated using the Birmingham Parallel Genetic Algorithm (BPGA). The effect of size and composition on the structures, stabilities and mixing properties of Ru–Pt nanoalloys are discussed. The results revealed that the maximum mixing tendency is achieved for 40–50% Ru compositions. Global minimum structures show that the Ru atoms prefer to occupy central and core positions and maximize coordination number and the number of strong Ru–Ru bonds.

The Birmingham Parallel Genetic Algorithm (BPGA) has been adopted for the global optimization of free and MgO(100)-supported Pd, Au and AuPd nanocluster structures, over the size range N = 4–10. Structures were evaluated directly using density functional theory, which has allowed the identification of Pd, Au and AuPd global minima. The energetics, structures, and tendency of segregation have been evaluated by different stability criteria such as binding energy, excess energy, second difference in energy, and adsorption energy. The ability of the approach in searching for putative global minimum has been assessed against a systematic homotop search method, which shows a high degree of success.