Regular Article

Positron binding to hydrocarbon molecules: calculation using the positron–electron correlation polarization potential

¹ Department of Chemistry, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama City, Saitama 338-8570, Japan
² Graduate School of Nanobioscience, Yokohama City University, 22-2 Seto Kanazawa-ku, Yokohama, Kanagawa 236-0027, Japan

^a e-mail: tako@mail.saitama-u.ac.jp

Received: 17 March 2019
Accepted: 22 May 2019
Published online: 6 August 2019

Abstract

Positron binding energies of naphthalene and alkanes (C_nH_2n+2 with n = 3 − 16) are calculated using the correlation polarization potential approach, where the short-range positron–electron correlation potential is modeled by the density-functional expression taken from a homogenous electron gas model. In the case of naphthalene, the calculated positron binding energy is found to reasonably agree with the experimental measurement. In the case of C_nH_2n+2 with the linear all-trans conformation we found positive positron binding energies for n ≥ 8 while the positron is not bound for n ≤ 7. This result cannot reproduce the previous experimental study, where the positron was bound for all alkanes with 3 ≤n ≤ 16. In addition, our calculated positron binding energies for n ≥ 9 are much larger than the experimental values although the generalized gradient approximation could improve the calculated values. We also investigated the conformer dependence of the positron binding energy for C₁₆H₃₄ and found that the positron binding energies significantly depend on the conformational structure; hairpin-like and crown-like structures generally have large positron binding energies, while single and multiple gauche structures have smaller binding energies.