Inorganics 2023, 11, 55. https://doi.org/10.3390/inorganics11020055 www.mdpi.com/journal/inorganics Article Simulation of a Single-Electron Device Based on Endohedral Fullerene (KI)@C180 Assel Istlyaup 1 , Ainur Duisenova 1 , Lyudmila Myasnikova 1 , Daulet Sergeyev 2 and Anatoli I. Popov 3, * 1 Department of Physics, K. Zhubanov Aktobe Regional University, Aktobe 030000, Kazakhstan 2 Department of Radio Electronics, T. Begeldinov Aktobe Aviation Institute, Aktobe 030012, Kazakhstan 3 Institute of Solid State Physics, University of Latvia, 8 Kengaraga, LV-1063 Riga, Latvia * Correspondence: popov@latnet.lv; Tel.: +371-29947899 Abstract: The progress of modern electronics largely depends on the possible emergence of previ- ously unknown materials in electronic technology. The search for and combination of new materials with extraordinary properties used for the production of new small-sized electronic devices and the improvement of the properties of existing materials due to improved technology for their manufac- ture and processing, in general, will determine the progress of highly promising electronics. In order to solve the problematic tasks of the miniaturization of electronic components with an increase in the level of connection of integrated circuits, new forms of electronic devices are being created using nanomaterials with controlled electrophysical characteristics. One of the unique properties of full- erene structures is that they can enclose one or several atoms inside their carbon framework. Such structures are usually called endohedral fullerenes. The electronic characteristics of endohedral full- erenes significantly depend on the properties of the encapsulated atom, which makes it possible to control them by choosing the encapsulated atom required by the property. Within the framework of the density functional theory in combination with the method of the nonequilibrium Green’s functions, the features of electron transport in fullerene nanojunctions were considered, which demonstrate “core–shell” nanoobjects, the “core” of which is an alkali halide crystal—KI—and the “shell” of which is an endohedral fullerene C180 located between the gold electrodes (in the nanogap). The values of the total energy and the stability diagram of a single-electron transistor based on endohedral fullerene (KI)@C180 were determined. The dependence of the total energy of fullerene molecules on the charge state is presented. The ranges of the Coulomb blockade, as well as their areas associated with the central Coulomb diamond were calculated. Keywords: endohedral; fullerene; density functional theory; KI; C180; single-electron device 1. Introduction Presently, it has become clear that the possibilities of silicon-based semiconductor electronics are limited. It turned out to be impossible to increase the speed of electronic systems and, at the same time, reduce the size and energy expended [1,2]. However, this problem can be solved by creating new materials for electronic technology. In this case, it is natural to first carry out the computer simulation and calculation of various electro- physical properties of new materials before starting their synthesis. To solve the problems of the miniaturization of electronic components with an increase in the degree of integra- tion of circuits, new types of electronic devices are being developed using nanomaterials with controlled electrophysical properties [3–5]. At present, the use of different types of carbon nanostructures in various areas of life, from the biomedical domain to solar energy, is widely known [6–17]. There are several works, both experimental [18–21] and using computer simulations [22,23], on the study of the crystallography of various alkali iodides grown in single-walled carbon nanotubes. Since single-walled carbon nanotubes have a relatively simple atomic structure with well- Citation: Istlyaup, A.; Duisenova, A.; Myasnikova, L.; Sergeyev, D.; Popov, A.I. Simulation of a Single-Electron Device Based on Endohedral Fullerene (KI)@C180. Inorganics 2023, 11, 55. https://doi.org/10.3390/ inorganics11020055 Academic Editor: Ian Dance Received: 10 November 2022 Revised: 25 December 2022 Accepted: 20 January 2023 Published: 24 January 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/license s/by/4.0/).