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Ab Initio Prediction of a Negative Barkas Coefficient for Slow Protons and Antiprotons in LiF

Qi, Xixi and Bruneval, Fabien and Maliyov, Ivan (2022) Ab Initio Prediction of a Negative Barkas Coefficient for Slow Protons and Antiprotons in LiF. Physical Review Letters, 128 (4). Art. No. 043401. ISSN 0031-9007. doi:10.1103/physrevlett.128.043401.

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We report the ab initio prediction of a negative Barkas coefficient in lithium fluoride (LiF) insulator at low velocity (v < 0.25 a. u., E_(kin) ∼ 2 keV). The electronic stopping power of protons in LiF has been extensively studied both experimentally and theoretically because of a controversial threshold effect. While our time-dependent density-functional theory simulations confirm the presence of a velocity threshold below which the proton stopping power vanishes, our calculations demonstrate that the antiprotons do not experience such a threshold. The combination of those two contrasting behaviors gives rise to an unprecedented negative Barkas effect: the stopping power of antiprotons is larger than that of protons. We identify that the slow antiproton at close encounter destabilizes a p orbital of the F⁻ anion pointing toward the antiproton. This particular orbital becomes highly polarizable and hence contributes much to the stopping power.

Item Type:Article
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URLURL TypeDescription
Qi, Xixi0000-0003-1507-8487
Bruneval, Fabien0000-0003-0885-8960
Maliyov, Ivan0000-0003-4130-6033
Additional Information:© 2022 American Physical Society. (Received 23 September 2021; accepted 5 January 2022; published 24 January 2022) This work was performed using HPC resources from GENCI-TGCC (Grant No. 2021-096018). We are indebted to I. Nagy for having pointed us to the LiF electronic stopping power.
Funding AgencyGrant Number
Grand Équipement National De Calcul Intensif2021-096018
Issue or Number:4
Record Number:CaltechAUTHORS:20220125-195124000
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:113102
Deposited By: George Porter
Deposited On:25 Jan 2022 21:58
Last Modified:25 Jan 2022 21:58

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