Maitrayee Ghosh

All Publications

• Light-enhanced oxygen degradation of MAPbBr3 single crystal. Physical chemistry chemical physics : PCCP Wang, K., Ecker, B. R., Ghosh, M., Li, M., Karasiev, V. V., Hu, S. X., Huang, J., Gao, Y. 2024

  Abstract

  Organometal halide perovskites are promising materials for optoelectronic applications, whose commercial realization depends critically on their stability under multiple environmental factors. In this study, a methylammonium lead bromide (MAPbBr3) single crystal was cleaved and exposed to simultaneous oxygen and light illumination under ultrahigh vacuum (UHV). The exposure process was monitored using X-ray photoelectron spectroscopy (XPS) with precise control of the exposure time and oxygen pressure. It was found that the combination of oxygen and light accelerated the degradation of MAPbBr3, which could not be viewed as a simple addition of that by oxygen-only and light-only exposures. The XPS spectra showed significant loss of carbon, bromine, and nitrogen at an oxygen exposure of 1010 Langmuir with light illumination, approximately 17 times of the additive effects of oxygen-only and light-only exposures. It was also found that the photoluminescence (PL) emission was much weakened by oxygen and light co-exposure, while previous reports had shown that PL was substantially enhanced by oxygen-only exposure. Measurements using a scanning electron microscope (SEM) and focused ion beam (FIB) demonstrated that the crystal surface was much roughened by the co-exposure. Density functional theory (DFT) calculations revealed the formation of superoxide and oxygen induced gap state, suggesting the creation of oxygen radicals by light illumination as a possible microscopic driving force for enhanced degradation.

  View details for DOI 10.1039/d3cp03493c

  View details for PubMedID 38258478

• Laser-direct-drive fusion target design with a high-Z gradient-density pusher shell. Physical review. E Hu, S. X., Ceurvorst, L., Peebles, J. L., Mao, A., Li, P., Lu, Y., Shvydky, A., Goncharov, V. N., Epstein, R., Nichols, K. A., Goshadze, R. M., Ghosh, M., Hinz, J., Karasiev, V. V., Zhang, S., Shaffer, N. R., Mihaylov, D. I., Cappelletti, J., Harding, D. R., Li, C. K., Campbell, E. M., Shah, R. C., Collins, T. J., Regan, S. P., Deeney, C. 2023; 108 (3-2): 035209

  Abstract

  Laser-direct-drive fusion target designs with solid deuterium-tritium (DT) fuel, a high-Z gradient-density pusher shell (GDPS), and a Au-coated foam layer have been investigated through both 1D and 2D radiation-hydrodynamic simulations. Compared with conventional low-Z ablators and DT-push-on-DT targets, these GDPS targets possess certain advantages of being instability-resistant implosions that can be high adiabat (α≥8) and low hot-spot and pusher-shell convergence (CR_{hs}≈22 and CR_{PS}≈17), and have a low implosion velocity (v_{imp}<3×10^{7}cm/s). Using symmetric drive with laser energies of 1.9 to 2.5MJ, 1D lilac simulations of these GDPS implosions can result in neutron yields corresponding to ≳50-MJ energy, even with reduced laser absorption due to the cross-beam energy transfer (CBET) effect. Two-dimensional draco simulations show that these GDPS targets can still ignite and deliver neutron yields from 4 to ∼10MJ even if CBET is present, while traditional DT-push-on-DT targets normally fail due to the CBET-induced reduction of ablation pressure. If CBET is mitigated, these GDPS targets are expected to produce neutron yields of >20MJ at a driven laser energy of ∼2MJ. The key factors behind the robust ignition and moderate energy gain of such GDPS implosions are as follows: (1) The high initial density of the high-Z pusher shell can be placed at a very high adiabat while the DT fuel is maintained at a relatively low-entropy state; therefore, such implosions can still provide enough compression ρR>1g/cm^{2} for sufficient confinement; (2) the high-Z layer significantly reduces heat-conduction loss from the hot spot since thermal conductivity scales as ∼1/Z; and (3) possible radiation trapping may offer an additional advantage for reducing energy loss from such high-Z targets.

  View details for DOI 10.1103/PhysRevE.108.035209

  View details for PubMedID 37849111

• Cooperative diffusion in body-centered cubic iron in Earth and super-Earths' inner core conditions. Journal of physics. Condensed matter : an Institute of Physics journal Ghosh, M., Zhang, S., Hu, L., Hu, S. X. 2023; 35 (15)

  Abstract

  The physical chemistry of iron at the inner-core conditions is key to understanding the evolution and habitability of Earth and super-Earth planets. Based on full first-principles simulations, we report cooperative diffusion along the longitudinally fast⟨111⟩directions of body-centered cubic (bcc) iron in temperature ranges of up to 2000-4000 K below melting and pressures of ∼300-4000 GPa. The diffusion is due to the low energy barrier in the corresponding direction and is accompanied by mechanical and dynamical stability, as well as strong elastic anisotropy of bcc iron. These findings provide a possible explanation for seismological signatures of the Earth's inner core, particularly the positive correlation between P wave velocity and attenuation. The diffusion can also change the detailed mechanism of core convection by increasing the diffusivity and electrical conductivity and lowering the viscosity. The results need to be considered in future geophysical and planetary models and should motivate future studies of materials under extreme conditions.

  View details for DOI 10.1088/1361-648X/acba71

  View details for PubMedID 36753774

• First-principles equation of state of CHON resin for inertial confinement fusion applications. Physical review. E Zhang, S., Karasiev, V. V., Shaffer, N., Mihaylov, D. I., Nichols, K., Paul, R., Goshadze, R. M., Ghosh, M., Hinz, J., Epstein, R., Goedecker, S., Hu, S. X. 2022; 106 (4-2): 045207

  Abstract

  A wide-range (0 to 1044.0 g/cm^{3} and 0 to 10^{9} K) equation-of-state (EOS) table for a CH_{1.72}O_{0.37}N_{0.086} quaternary compound has been constructed based on density-functional theory (DFT) molecular-dynamics (MD) calculations using a combination of Kohn-Sham DFT MD, orbital-free DFT MD, and numerical extrapolation. The first-principles EOS data are compared with predictions of simple models, including the fully ionized ideal gas and the Fermi-degenerate electron gas models, to chart their temperature-density conditions of applicability. The shock Hugoniot, thermodynamic properties, and bulk sound velocities are predicted based on the EOS table and compared to those of C-H compounds. The Hugoniot results show the maximum compression ratio of the C-H-O-N resin is larger than that of CH polystyrene due to the existence of oxygen and nitrogen; while the other properties are similar between CHON and CH. Radiation hydrodynamic simulations have been performed using the table for inertial confinement fusion targets with a CHON ablator and compared with a similar design with CH. The simulations show CHON outperforms CH as the ablator for laser-direct-drive target designs.

  View details for DOI 10.1103/PhysRevE.106.045207

  View details for PubMedID 36397594

• Pseudo-Jahn-Teller effects in two-dimensional silicene, germanene and stanene: a crystal orbital vibronic coupling density analysis BULLETIN OF MATERIALS SCIENCE Ghosh, M., Datta, A. 2018; 41 (5)

  View details for DOI 10.1007/s12034-018-1634-y

  View details for Web of Science ID 000442546900001