PSI - Issue 68

D.M. Tshwane et al. / Procedia Structural Integrity 68 (2025) 39–46 D.M. Tshwane et al. / Structural Integrity Procedia 00 (2025) 000–000

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The adsorption energy presented in Fig. 2 (b) is a function of the coverage of H on the surface of Ti 2 AlV (110) used to investigate the effect of the adsorption strength. At low coverage, it was observed that hydrogen atoms prefer to adsorb on the surface of Ti 2 AlV (110). The adsorption energy strength increases as hydrogen coverage changes from 1 to 4 per H atom content, which suggests a stronger and energetically favourable interaction. Fig. 3 shows a clear relationship between adsorption energy and H content atom; the adsorption energy configuration for n = 3 is greater ( !) "* # +,) -12,752 eV and !) "* # + = -12,457 eV) than for n = 2 ( !) "* # +,) = -8,882 eV and !) "* # + = -8,640 eV) and lower for n = 4 ( !) "* # +,) = -17,134 eV and !) "* # + = -16,917 eV). The scenario for coverage adsorption is energetically stable, with preferential coverage of four H atoms on the surface of Ti 2 AlV. However, it is worth mentioning that the coverage adsorption may depend on the size and potential adsorption site of the surface. 3.2. Work function The work function, also known as the electrostatic potential, describes the minimum amount of energy required to remove or extract an electron from a crystal surface in a vacuum. This is the most basic crystal solid surface characteristic for understanding a wide range of structural, physical, and chemical surface properties. Additionally, comprehending the atomic interaction in the adsorption system requires an understanding of the work function. The work function in the adsorption system is essential for comprehending atomic interactions. The work function is calculated using Eq. 2: ɸ=ɸ -!. − * (2) where ɸ -!. represents the electrostatic potential energy of the vacuum while * refers to the Fermi energy level. The calculated work function of the adsorbates at various adsorption sites is shown in Fig. 3. It was discovered that the numerical value of the work function increases after hydrogen is adsorbed on the surface of Ti 2 AlV (110) as opposed to the pure surface with 3.506 eV (Tshwane and Modiba, 2023). A dipole on the adsorbate with a negative charge causes the induced work function, and the adsorbate atom determines how much of an induced work function. Moreover, it was observed that the numerical work function value varies with the adsorption site, wherein the Ti and Al-V sites show a high and a low work function value, respectively.

Fig. 3. Work function at different adsorption sites on the Ti 2 Al (110) surface after hydrogen adsorption.