Seminar by Dr. Fadjar Mulya and Dr. Warin Rangubpit

On November 8, 2024, the lectures from Dr. Fadjar Mulya and Dr. Warin Rangubpit takes place on the 5th Floor of the Library with detailed content as follows:

Dr. Fadjar Mulya presents about "DFT study of lithium adsorption on silicon quantum dots for battery applications"

Abstract:

Understanding lithium (Li) adsorption in silicon quantum dots (SiQDs) is crucial for optimizing Li-ion battery (LIB) anode materials. We systematically investigated Li adsorption in ten hydrogenated SiQDs (Si10H16, Si14H20, Si18H24, Si22H28, Si26H30, Si30H34, Si35H36, Si39H40, Si44H42, and Si48H46) across five adsorption sites (bridge(B), on-top(T), hollow-tetrahedral inner(Tdinner), hollow-tetrahedral surface(Tdsurface), and hollow-hexagonal(Hex)), utilizing density functional theory (DFT) with the M06–2X hybrid functional and 6-31G+(d) basis set. Findings identify Tdinner as the most favorable adsorption site, with a binding energy (Ebind) of 0.80–1.00 eV, dependent on SiQD size. The adsorption site exerts a more pronounced impact on Ebind than the cluster size. Multiple adsorptions in SiQDs show increased Ebind per Li atom with Li atom number. Molecular volume changes, independent of Li atom number but site-dependent, exhibit a maximum of 2.51 %. SiQD energy gap, influencing conductivity, varies with size, larger SiQDs being more conductive, especially with Li adsorption. Conclusively, our study recommends large-sized SiQDs as optimal LIB anode materials, offering high capacity, minimal volume expansion, and reasonable conductivity. This research addresses a theoretical gap, illuminating the impact of Li adsorption on SiQD molecular volumes and electronic structures, aiding in the design of enhanced capacity silicon anodes for LIB.

Dr. Warin Rangubpit presents about "Pore Formation by Amyloid-like Peptides: Effects of the Nonpolar–Polar Sequence"

Abstract:

One of the mechanisms accounting for the toxicity of amyloid peptides in diseases like Alzheimer’s and Parkinson’s is the formation of pores on the plasma membrane of neurons. Here, we perform unbiased all-atom simulations of the full membrane damaging pathway, which includes adsorption, aggregation, and perforation of the lipid bilayer accounting for pore-like structures. Simulations are performed using four peptides made with the same amino acids. Differences in the nonpolar–polar sequence pattern of these peptides prompt them to adsorb into the membrane with the extended conformations oriented either parallel [peptide labeled F1, Ac-(FKFE)2-NH2], perpendicular (F4, Ac-FFFFKKEE-NH2), or with an intermediate orientation (F2, Ac-FFKKFFEE-NH2, and F3, Ac-FFFKFEKE-NH2) in regard to the membrane surface. At the water–lipid interface, only F1 fully self-assembles into β-sheets, and F2 peptides partially fold into an α-helical structure. The β-sheets of F1 emerge as electrostatic interactions attract neighboring peptides to intermediate distances where nonpolar side chains can interact within the dry core of the bilayer. This complex interplay between electrostatic and nonpolar interactions is not observed for the other peptides. Although β-sheets of F1 pe