skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Optical properties of highly compressed polystyrene: An ab initio study

Abstract

Using all-electron density functional theory, we have performed an ab initio study on x ray absorption spectra of highly compressed polystyrene (CH). Here, we found that the K-edge shifts in strongly coupled, degenerate polystyrene cannot be explained by existing continuum-lowering models adopted in traditional plasma physics. To gain insights into the K edge shift in warm, dense CH, we have developed a model designated as “single-mixture-in-a-box” (SMIAB), which incorporates both the lowering of continuum and the rising of Fermi surface resulting from high compression. This simple SMIAB model correctly predicts the K-edge shift of carbon in highly compressed CH in good agreement with results from quantum-molecular-dynamics (QMD) calculations. Traditional opacity models failed to give the proper K-edge shifts as the CH density increased. Based on QMD calculations, we have established a first-principles opacity table (FPOT) for CH in a wide range of densities and temperatures [p = 0.1 to 100 g/cm 3 and T = 2000 to 1,000,000 K]. The FPOT gives much higher Rosseland mean opacity compared to the cold-opacity–patched astrophysics opacity table for warm, dense CH and favorably compares to the newly improved Los Alamos ATOMIC model for moderately compressed CH (pCH ≤10 g/cm 3) but remains amore » factor of 2 to 3 higher at extremely high densities (pCH ≥ 50 g/cm 3). We anticipate the established FPOT of CH will find important applications to reliable designs of high-energy-density experiments. Moreover, the understanding of K-edge shifting revealed in this study could provide guides for improving the traditional opacity models to properly handle the strongly coupled and degenerate conditions.« less

Authors:
 [1];  [2];  [2];  [1];  [2]
  1. Univ. of Rochester, NY (United States). Lab. for Laser Energetics
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Univ. of Rochester, NY (United States). Lab. for Laser Energetics
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1399472
Report Number(s):
2017-98; 1354
Journal ID: ISSN 2469-9950; PRBMDO; 2017-98, 2309, 1354
Grant/Contract Number:
NA0001944; AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 96; Journal Issue: 14; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; cs.DB; H.2.8

Citation Formats

Hu, S. X., Collins, L. A., Colgan, J. P., Goncharov, V. N., and Kilcrease, D. P.. Optical properties of highly compressed polystyrene: An ab initio study. United States: N. p., 2017. Web. doi:10.1103/PhysRevB.96.144203.
Hu, S. X., Collins, L. A., Colgan, J. P., Goncharov, V. N., & Kilcrease, D. P.. Optical properties of highly compressed polystyrene: An ab initio study. United States. doi:10.1103/PhysRevB.96.144203.
Hu, S. X., Collins, L. A., Colgan, J. P., Goncharov, V. N., and Kilcrease, D. P.. 2017. "Optical properties of highly compressed polystyrene: An ab initio study". United States. doi:10.1103/PhysRevB.96.144203.
@article{osti_1399472,
title = {Optical properties of highly compressed polystyrene: An ab initio study},
author = {Hu, S. X. and Collins, L. A. and Colgan, J. P. and Goncharov, V. N. and Kilcrease, D. P.},
abstractNote = {Using all-electron density functional theory, we have performed an ab initio study on x ray absorption spectra of highly compressed polystyrene (CH). Here, we found that the K-edge shifts in strongly coupled, degenerate polystyrene cannot be explained by existing continuum-lowering models adopted in traditional plasma physics. To gain insights into the K edge shift in warm, dense CH, we have developed a model designated as “single-mixture-in-a-box” (SMIAB), which incorporates both the lowering of continuum and the rising of Fermi surface resulting from high compression. This simple SMIAB model correctly predicts the K-edge shift of carbon in highly compressed CH in good agreement with results from quantum-molecular-dynamics (QMD) calculations. Traditional opacity models failed to give the proper K-edge shifts as the CH density increased. Based on QMD calculations, we have established a first-principles opacity table (FPOT) for CH in a wide range of densities and temperatures [p = 0.1 to 100 g/cm3 and T = 2000 to 1,000,000 K]. The FPOT gives much higher Rosseland mean opacity compared to the cold-opacity–patched astrophysics opacity table for warm, dense CH and favorably compares to the newly improved Los Alamos ATOMIC model for moderately compressed CH (pCH ≤10 g/cm3) but remains a factor of 2 to 3 higher at extremely high densities (pCH ≥ 50 g/cm3). We anticipate the established FPOT of CH will find important applications to reliable designs of high-energy-density experiments. Moreover, the understanding of K-edge shifting revealed in this study could provide guides for improving the traditional opacity models to properly handle the strongly coupled and degenerate conditions.},
doi = {10.1103/PhysRevB.96.144203},
journal = {Physical Review B},
number = 14,
volume = 96,
place = {United States},
year = 2017,
month =
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on October 16, 2018
Publisher's Version of Record

Save / Share:
  • Atomic and electronic structure, and diffusion coefficients in liquid Ni-Al alloys, have been calculated by ab initio molecular-dynamics simulations. The chemically short-range ordered structure of liquid Ni{sub 20}Al{sub 80} measured by neutron scattering is well reproduced in these simulations. We calculate a significant electronic contribution ({Delta}S{sub el}=-0.4 k{sub B}/atom) to the formation entropy of NiAl at 1900 K, originating from a simultaneous narrowing and shifting of the Ni d band to higher binding energies accompanying alloying with Al. This value of {Delta}S{sub el}, combined with an estimate for the configurational entropy based on calculated radial distribution functions and a nonadditivemore » hard-sphere model, accounts for the large negative excess entropy of mixing measured in liquid Ni-Al alloys.« less
  • We have performed quantum molecular dynamic simulations for warm dense polystyrene at high pressures. The principal Hugoniot up to 770 GPa is derived from wide range equation of states. The optical conductivity is calculated via the Kubo-Greenwood formula, from which the dc electrical conductivity and optical reflectivity are determined. The nonmetal-to-metal transition is identified by gradual decomposition of the polymer. Our results show good agreement with recent high precision laser-driven experiments.
  • We present an {ital ab} {ital initio} molecular-dynamics study of III-V hydrogenated microclusters with the purpose of identifying stable and optically active structures suitable for inclusion in zeolite cages. We find that the most stable and optically active clusters are distorted tetrahedral structures with a majority of atoms of group V. Cubic clusters show unexpected structural stability, but with negligible matrix element for optical transitions close to the energy gap. Our results are compatible with existing experimental data.
  • The equation of state and optical properties of shocked LiF are investigated using quantum molecular dynamics (QMD) in a wide range of pressures and temperatures along the principal Hugoniot. These simulations are bridging the gap between shock experiments up to 2 Mbars and recent laser shock experiments beyond 6 Mbars. We find that the melting of LiF corresponds to an increase in absorption which is later followed by an increase in reflectivity. The reflectivities computed at high pressures are in close agreement with the experimental measurements but with Hugoniot conditions at much lower temperatures and pressures than measured experimentally. Finally,more » we provide a simple fit to the variation of the QMD index of refraction for pressures above 1.5 Mbars.« less