Journal: Journal of Bangladesh Chemical Society , Publisher: Bangladesh Chemical Society,

Abstract: Infrared (IR) photodissociation spectra of adenine-thymine (AT +) hetero-dimer cluster has been recorded in the region of 2900-3700 cm-1 in order to investigate the most stable conformer of adenine-thymine hetero-dimer. A new conformer (conformer I) was found which is more stable by 285, 221 and 312 cm-1 than the Watson-Crick conformer (conformer II) at DFT/B3LYP/cc-pVTZ, DFT/M06-2X/cc-pVTZ and DFT/wB97XD/cc-pVTZ levels of theory, respectively. DFT calculated vibration spectra of both conformer I and II shows good agreement with the experimental vibrational spectrum of isolated AT + base pair. According to very high level quantum chemical calculations, it is noticeable that the Watson-Crick conformer of AT base pair is not the most stable conformer in gas phase.

Journal: Journal of Bangladesh Chemical Society, Publisher: Bangladesh Chemical Society 

Abstract: Reducing the head-media spacing is of crucial importance in enabling future high-density magnetic recording. In this work,we have studied the effect of nitrogen incorporation and ultraviolet (UV) irradiation on the interaction between the perfluoropolyether (PFPE) to the carbon surface using quantum chemical method. This paper explores that the UV bonding of PFPE Z-tetraol molecule significantly changes their structural and electronic properties. The results showed that the UV irradiation significantly strengthens bonding of PFPE on carbon surfaces. It is also found that nitrogen incorporation changes the structural and chemical properties of carbon surface and enhanced the bonding between PFPE and carbon surface.

Journal: Bangladesh Journal of Physics, Publisher: Bangladesh Physical Society, 

Abstract:In this work, molecular dynamics (MD) study of triglyme (G3) solution containing lithium bis (trifluoro methyl sulfonyl) amide (Li[TFSA]) were investigated using classical atomistic force fields. G3 is a typical solvent used in non-aqueous Li-air battery. It shows here coordination of Li+ with G3 and [TFSA]- does not significantly change with increasing the concentration of G3 but self-diffusion coefficient of all the ions increases with increasing G3 concentration. The density of [Li(G3)[TFSA] complex decreases with increasing G3 concentration which lead to accelerate diffusivity of ions.

Journal: Bangladesh Journal of Physics, Publisher: Bangladesh Physical Society, 

Abstract:Terahertz (THz) absorption spectra of poly 3-hydroxyalkanoates (PHB) for different conformations were investigated using molecular dynamics (MD) method. Temperature-dependent THz absorption spectra of PHB were measured over a temperature range of 10 K to 200 K. Peaks around (2.4-2.6THz) and (3.1-3.2THz) were observed due to vibrational transition of PHB, 1stpeaks are polarized perpendicular to c(┴)axis (along a, b axis) and next peaks are oriented parallel to the c(//) axis. The peak around (2.4-2.6THz) was assigned due to vibrational transition of PHB and C-H…O=C hydrogen bonds are oriented perpendicular to the c(┴) axis. We have also investigated orientation of the intermolecular hydrogen bonds by MD simulation and confirmed that it was mainly along the b axis of PHB. THz absorption spectra shifted to the lower frequencies and noticed widening of the absorption peaks that visualized from characteristics of peaks within creasing temperature, which is well reproduce of experimental observation. Bangladesh Journal of Physics, 26(2), 21-31, December 2019

Journal: Barishal University Jounal of Science and Engineering 

Journal: PhysicalChemistryChemicalPhysics  Publisher: Royal Society of Chemistry, Ranking: Q1 , IF=2.9

Abstract: Predicting electronically excited states across electron-donor/electron acceptor interfaces is essential for understanding the charge photogeneration process in organic solar cells. However, organic solar cells are large and disordered systems, and their excited states cannot be easily accessed by conventional quantum chemistry approaches. Moreover, a large number of excited states must be obtained to fully understand the charge separation mechanism. Recently, we have developed a novel fragment-based excited state method which can efficiently calculate a large number of states in molecular aggregates. In this article, we demonstrate the large-scale excited-state calculations by investigating interfacial charge transfer (ICT) states across the electron-donor/electron acceptor interfaces. As the model systems, we considered the face-on and edge-on configurations of pentacene/C60 bilayer heterojunction structures. These model structures contain approximately 1.8 × 105 atoms, and their local interface regions containing 2000 atoms were treated quantum mechanically, embedded in the electrostatic potentials from the remaining parts. Therefore, the charge delocalization effect, structural disorder, and the resulting heterogeneous electrostatic and polarizable environments were taken into account in the excited-state calculations. The computed energies of the low-lying ICT states are in reasonable agreement with experimental estimates. By comparing the edge-on and face-on configurations of the pentacene/C60 interfaces, we discuss the influence of interfacial morphologies on the energetics and charge delocalization of ICT states. In addition, we present the detailed characterization of excited states and highlight the importance of hybridization effects between pentacene excited states and ICT states. The large-scale ab initio calculations for the interface systems enabled the exploration of the ICT states, leading to first-principles investigation of the charge separation mechanism in organic solar cells.

Journal: MRS Communications, Publisher: Springer Nature, Ranking: Q2  IF=2.3 

Abstract: We have investigated the equilibrium conformation of Pt2Ru3 nanoparticles in the presence of H2 and CO mixture gas using density functional theory (DFT) and Monte Carlo (MC) simulation. A multiple linear regression equation was prepared using DFT results to calculate adsorption energy from the structural descriptors. Using the regression equation, MC simulations were employed to elucidate the equilibrated conformation of Pt2Ru3 particles at a finite temperature of H2/CO where CO concentration in the range 100-500 ppm. MC results indicate that CO/H2 coadsorption induced the rearrangement of alloying atoms and Pt/Ru ratio exposed to the surface decreases with the increase of CO concentration.

Dr. Md. Shakhawat Hossain,  The power of livestreaming: Will it become an alternative strategy for startups?, Scopus (Q1), SSCI, Elsevier

Application of the SOBC model to study customers' online purchase intentions in an emerging economy during COVID-19: does gender matter? Scopus (Q1), Emerald, Prince sultan university,