Interaction of low-energy ions and atoms of light elements with a fluorinated carbon molecular lattice

低エネルギー軽元素イオン・原子とフッ化炭素分子格子との相互作用

Avramov, P.; Yakobson, B. I.*

Avramov, P.; Yakobson, B. I.*

2-40eV H, H, He, LiとCH, CF, C, CF分子との相互作用を非経験的分子動力学シミュレーションと量子化学計算を使って研究した。"CH + H"と"C + H"においては、芳香族分子からHへの電荷移行が1に近い確率で起こり、この過程によりHは水素原子に、中性のCHとCはカチオンラジカルになる。低エネルギーHとCF, CFとの相互作用はこれとは本質的に異なり、定性的には中性分子と点電荷との相互作用として考えることができる。補償していないHの電荷とフッ素原子のマリケン電荷との相互作用から生じるクーロン摂動によって、H、及びCF, CFに局在する電子状態のエネルギーが反転し、その結果、エネルギー的に不利になるため電荷移行は起こらない。また、Hの透過に対するCFとCFのポテンシャルバリアーは、CHとCの場合に比べて2-4倍低い。He原子とLiイオンの透過に対するバリアーはおもに入射粒子の実効半径に依存する。

The mechanism of interaction of low-energy atoms and ions of light elements (H, H, He, Li, the kinetic energy of the particles 2-40 eV) with CH, CF, C, and CF molecules was studied by ab initio MD simulations and quantum chemical calculations. It was shown that for the "CH + proton" and "C + proton" systems, the electronic charge transfer from the aromatic molecule to H occurs with a probability close to 1. The process transforms the H to a hydrogen atom and the neutral CH and C molecules to cation radicals. The mechanism of interaction of low-energy protons with CF and CF molecules has a substantially different character and can be considered qualitatively as the interaction between a neutral molecule and a point charge. The Coulomb perturbation of the system arising from the interaction of the uncompensated proton charge with the Mulliken charges of fluorine atoms results in an inversion of the energies of the electronic states localized on the proton and on the CF and CF molecules and makes the electronic charge transfer energetically unfavorable. The barriers of the proton penetration for the CF and CF molecules are from two to four times lower than for the corresponding parent systems (CH and C). The penetration barriers of the He atom and Li ion depend mainly on the effective radii of the bombarding particles.