# Applied Materials Science Lab

# Anh D. Phan, Dr.

Group leader

Faculty of Materials Science and Engineering

Room 702, Building A5, Phenikaa University,

Yen Nghia Ward, Ha Dong District, Hanoi, Vietnam.

Email: anh.phanduc@phenikaa-uni.edu.vn

**NEWS**

*6/10/2021 - *Cuong attended the online conference held from 4 October 2021 to 6 October 2021 in Hanoi, Vietnam.

*28/9/2021* - The paper "*Effects of surface charge and environmental factors on the electrostatic interaction of fiber with virus-like particle: A case of coronavirus*" is accepted for publication in AIP Advances.

We propose a theoretical model to elucidate intermolecular electrostatic interactions between a virus and a substrate. Our model treats the virus as a homogeneous particle having surface charge and the polymer fiber of the respirator as a charged plane. Electric potentials surrounding the virus and fiber are influenced by the surface charge distribution of the virus. We use Poisson-Boltzmann equations to calculate electric potentials. Then, Derjaguin's approximation and a linear superposition of the potential function are extended to determine the electrostatic force. In this work, we apply this model for coronavirus or SARS-CoV-2 case and numerical results quantitatively agree with prior simulation. We find that the influence of fiber's potential on the surface charge of the virus is important and is considered in interaction calculations to obtain better accuracy. The electrostatic interaction significantly decays with increasing separation distance, and this curve becomes steeper when adding more salt. Although the interaction force increases with heating, one can observe the repulsive-attractive transition when the environment is acidic.

*2**6**/**7**/2021* - The paper "*Toward a better understanding of activation volume and dynamic decoupling of glass-forming liquids under compression*" is accepted for publication in Macromolecular Theory and Simulation.

Physical properties of the pressure-induced activation volume and dynamic decoupling of ternidazole, glycerol, and probucol by the elastically collective nonlinear Langevin equation theory is theoretically investigated. Based on the predicted temperature dependence of activated relaxation under various compressions, the activation volume is determined to characterize effects of pressure on molecular dynamics of materials. It is found that the decoupling of the structural relaxation time of compressed systems from their bulk uncompressed value is governed by the power-law rule. The decoupling exponent exponentially grows with pressure below 2 GPa. The decoupling exponent and activation volume are intercorrelated and have a connection with the differential activation free energy. Relationships among these quantities are analyzed numerically and mathematically to explain many results in previous experiments and simulations.

*21/2/2021* - We theoretically investigate high-pressure effects on the atomic dynamics of metallic glasses. The theory predicts compression-induced rejuvenation and the resulting strain hardening that have been recently observed in metallic glasses. Structural relaxation under pressure is mainly governed by local cage dynamics. The external pressure restricts the dynamical constraints and slows down the atomic mobility. In addition, the compression induces a rejuvenated metastable state (local minimum) at a higher energy in the free-energy landscape. Thus, compressed metallic glasses can rejuvenate and the corresponding relaxation is reversible. This behavior leads to strain hardening in mechanical deformation experiments. Theoretical predictions agree well with experiments.

*19/12/2021* - Iron represents the principal constituent of the Earth's core, but its high-pressure melting diagram remains ambiguous. Here we present a simple analytical approach to predict the melting properties of iron under deep-Earth conditions. In our model, anharmonic free energies of the solid phase are directly determined by the moment expansion technique in quantum statistical mechanics. This basis associated with the Lindemann criterion for a vibrational instability can deduce the melting temperature. Moreover, we correlate the thermal expansion process with the shear response to explain a discontinuity of atomic volume, enthalpy, and entropy upon melting. Our numerical calculations are quantitatively consistent with recent experiments and simulations. The obtained results would improve understanding of the Earth's structure, dynamics, and evolution.

I am looking for several undergraduate and graduate students, and postdocs in the areas of energy, surface science and engineering, interfacial phenomena, pharmaceutics, and machine learning for materials science.

Contact me if you are interested in my research!