Table of contents

The 47th Vietnam Conference on Theoretical Physics (VCTP-47) was held during 1-4 August 2022 in Tuy Hoa city, Phu Yen province, Viet Nam.

The VCTP-47 was organized by the Institute of Physics, Vietnam Academy of Science and Technology (VAST) under the auspices of the Vietnamese Theoretical Physics Society (VTPS).

The VCTP, formerly known as NCTP, has been an annual activity of VTPS since 1976. The VCTP is aimed to be an international conference for physicists in Vietnam, in the region and worldwide. Our mission is to foster scientific exchanges and to promote a high-standard level of research and education in Vietnam and in South East Asia.

The conference covered a wide range of theoretical physics topics from 4 major fields:

• Particle, nuclear and astro-physics,

• Molecular physics, quantum optics and quantum computation,

• Condensed matter physics,

• Soft matter, biological and interdisciplinary physics.

The conference was divided into 1 opening session, 9 oral sessions and 2 poster sessions. The duration of an invited talk is 30-40 minutes including time for discussion. The duration of an oral talk is 20 minutes including time for discussion.

The meeting was held onsite but all the sessions were broadcasted online on the Google Meet platform. There was only one fully online session with three invited speakers presenting their talks from abroad. For online viewing, the PDF files of the posters had be uploaded on to the conference website before the poster sessions.

136 participants participated in the conference. 11 invited talks, 17 oral and 55 poster contributions were presented. The conference program and the abstract book can be found on the conference website: http://iop.vast.vn/vctp/47/.

This volume contains selected papers contributed by the participants.

We gratefully acknowledge the financial support of the Unesco's Category 2 International Centre of Physics (ICP) located at the Institute of Physics, VAST.

Editors of the VCTP-47 Proceedings

Trinh Xuan Hoang, Tran Minh Tien, Hoang Anh Tuan, and Vu Ngoc Tuoc

List of Organizer, Sponsor, Chair, Organizing Committee, Program Committee, Secretariat, Participants are available in this Pdf.

All papers published in this volume have been reviewed through processes administered by the Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

• Type of peer review: Single Anonymous

• Conference submission management system: Morressier

• Number of submissions received: 11

• Number of submissions sent for review: 10

• Number of submissions accepted: 6

• Acceptance Rate (Submissions Accepted / Submissions Received × 100): 54.5

• Average number of reviews per paper: 1

• Total number of reviewers involved: 10

• Contact person for queries:

Name: Hoang Anh Tuan

Email: hatuan@iop.vast.vn

Affiliation: Institute of Physics, Vietnam Academy of Science and Technology

One-loop on-shell and off-shell decays H → VV with VV = γγ, Zγ, ZZ are presented in this paper. The effects of one-loop on-shell and off-shell Higgs decays via Higgs productions at future lepton colliders are also then examined. We find that the impacts of one-loop Higgs decays are significant and they are should be taken into account at future lepton colliders.

A first-principle study of the structural diversity and optoelectronic properties of the small penta-graphene quantum dots (PGQDs) has been performed. The stability and optoelectronic properties of the PGQDs are investigated under the effect of chemical modifications. PGQDs are edge functionalized by non-metallic atoms (Si, P, O, F) such as identical edge termination (Si-PGQD, P-PGQD, O-PGQD, F-PGQD) and alternate edge termination (Si-O-PGQD, H-P-PGQD). Further, H-PGQDs are also doped and co-doped with B and P atoms. All studied structures are stable with strong electronic quantization and exhibit semiconducting or metallic properties depending on the termination, doping elements and their site. Absorption peaks in the visible region were not observed for hydrogen passivation PGQDs. However, some absorption peaks appear in this region for edge-passivated. In addition, there are dramatic changes in the electronic properties of B, P, BP-doped PGQDs to give peak shifts to the visible region from the ultraviolet region of the pure sample due to hybridization effects. The enhanced reactivity, controllable electronic properties of edge passivation, and doping make PGQDs ideal for new nanodevice applications.

We propose a theoretical model to investigate photothermal heating of ultra-flexible metamaterials, which are obtained by randomly mixing TiN nanoparticles in polydimethylsiloxane (PDMS). Due to the plasmonic properties of TiN nanoparticles, incident light can be perfectly absorbed in a broadband range (300-3000 nm) to generate heat within these metamaterials. Under irradiation of an 808 nm near-infrared laser with different intensities, our predicted temperature rises as a function of time agree well with recent experimental data. For a given laser intensity, the temperature rise varies non-monotonically with the concentration of TiN nanoparticles. Increasing the TiN concentration leads to a decrease in the heating process since the thermal conductivity grows. A small TiN concentration significantly reduces the absorbed energy and, thus, the system is less heated. When we apply this model to solar heating, we find that the temperature rise is no longer non-monotonic, and the heating efficiency is much lower than in the laser case. Our studies would provide good guidance for future experimental studies on the photothermal heating of broadband perfect absorbers.

We study metal-insulator phase diagram in the half-filled disordered Hubbard model at finite temperature. We calculate the averaged local density of states at the Fermi level and the site occupation as a function of the on-site energy at finite temperature by using typical medium theory with an impurity solver of equation of motion method. Although the metallicity in the correlated metallic region changes with temperature change, the phase diagram is almost temperature independent. We find fairly good agreement between our site occupation and those obtained by the typical medium method with other impurity solver.

In this work, we performed a density functional theory calculation to systematically investigate the adsorption and evaluate the adsorption performance of aromatic volatile organic compounds, benzene and toluene, on WSe₂ monolayer. The most favourable adsorption configurations of gas molecules with the parallel orientation of the benzene ring to the substrate surface are explored by computing the binding energies as a function of spatial coordinates and carefully optimizing geometrical structures. The calculations pointed out that gas molecules could diffuse across the substrate along the diffusion paths with quite low diffusion potential barriers, about 180 meV for benzene and 130 meV for toluene molecules. We found that both gases are physisorbed on WSe₂ monolayer with moderate adsorption energies, short recovery times, and large response lengths. The gas adsorption causes the bandgap reduction of 26 meV and a slight work function increase of the substrate. There is a charge transfer from the substrate onto the gas molecules, this may cause a resistance decrease of the p-type semiconductor substrate. WSe₂ monolayer is quite sensitive to benzene and toluene, and could be suggested as an aromatic gas sensing material.

The SARS-CoV-2 main protease (Mpro) plays an important role in the viral transcription and replication of the SARS-CoV-2 virus that is causing the Covid-19 pandemic worldwide. Therefore, it represents a very attractive target for drug development for treatment of this disease. It is a cysteine protease because it has in the active site the catalytic dyad composed of cysteine (C145) and histidine (H41). The catalytic site represents the binding site for inhibitors, many of them bind to Mpro with a covalent bond. In this research, structural and physiochemical characteristics of the Mpro binding site are investigated when the ligand 11a is covalently and non-covalently bound. All-atom molecular dynamics (MD) simulations were run for 500 ns at physiological temperature (310 K). It is found that conformations of both the Mpro protein and the ligand are stable during the simulation with covalently bound complex showing stronger stability. When the ligand is covalently bound (its final state), residues that stably interact with the ligand are H41, C145, H163, H164 and E166. The optimal conformation of these residues is stabilized also via the Hbond interactions with the catalytic water present in the Mpro binding site. In the case of the non-covalently bound ligand (state before the covalent bond is formed), the binding site residues retain their conformations similar to the covalent binding site, and they still form Hbonds with the catalytic water, except H41. This residue, instead, adopts a different conformation and looses the Hbond with the catalytic water, leaving more freedom to move to the ligand. We hypothesize that H41 could play a role in guiding the ligand to the optimal position for final covalent bonding. Further analyses are in process to check this hypothesis. These results represent an important basis for studying drug candidates against SARS-CoV-2 by means of computer aided drug design.