Morinson-Negrete Juan David, Ortega-López César, Espitia-Rico Miguel J
Grupo Avanzado de Materiales y Sistemas Complejos GAMASCO, Universidad de Córdoba, Montería CP 230001, Colombia.
Doctorado en Ciencias Física, Universidad de Córdoba, Montería CP 203001, Colombia.
Materials (Basel). 2022 Apr 8;15(8):2731. doi: 10.3390/ma15082731.
The effects of the monovacancies of oxygen (VO) and manganese (VMn) on the structural and electronic properties of the 1T−MnO2/graphene heterostructure are investigated, within the framework of density functional theory (DFT). We found that the values of the formation energy for the heterostructure without and with vacancies of VO and VMn were −20.99 meVÅ2 , −32.11meVÅ2, and −20.81 meVÅ2, respectively. The negative values of the formation energy indicate that the three heterostructures are energetically stable and that they could be grown in the experiment (exothermic processes). Additionally, it was found that the presence of monovacancies of VO and VMn in the heterostructure induce: (a) a slight decrease in the interlayer separation distance in the 1T−MnO2/graphene heterostructure of ~0.13% and ~1.41%, respectively, and (b) a contraction of the (Mn−O) bond length of the neighboring atoms of the VO and VMn monovacancies of ~2.34% and ~6.83%, respectively. Calculations of the Bader charge for the heterostructure without and with VO and VMn monovacancies show that these monovacancies induce significant changes in the charge of the first-neighbor atoms of the VO and VMn vacancies, generating chemically active sites (locales) that could favor the adsorption of external atoms and molecules. From the analysis of the density of state and the structure of the bands, we found that the graphene conserves the Dirac cone in the heterostructure with or without vacancies, while the 1T−MnO2 monolayer in the heterostructures without and with VO monovacancies exhibits half-metallic and magnetic behavior. These properties mainly come from the hybridization of the 3d−Mn and 2p−O states. In both cases, the heterostructure possesses a magnetic moment of 3.00 μβ/Mn. From this behavior, it can be inferred the heterostructures with and without VO monovacancies could be used in spintronics.
在密度泛函理论（DFT）框架下，研究了氧单空位（VO）和锰单空位（VMn）对1T−MnO₂/石墨烯异质结构的结构和电子性质的影响。我们发现，不含空位、含有VO空位和含有VMn空位的异质结构的形成能值分别为−20.99 meVŲ、−32.11 meVŲ和−20.81 meVŲ。形成能的负值表明这三种异质结构在能量上是稳定的，并且它们可以在实验中生长（放热过程）。此外，还发现异质结构中VO和VMn单空位的存在会导致：（a）1T−MnO₂/石墨烯异质结构中层间分离距离分别略有减小，约为0.13%和1.41%，以及（b）VO和VMn单空位相邻原子的（Mn−O）键长分别收缩约2.34%和6.83%。对不含空位、含有VO和VMn单空位的异质结构的巴德电荷计算表明，这些单空位会导致VO和VMn空位的第一近邻原子的电荷发生显著变化，产生有利于外部原子和分子吸附的化学活性位点（区域）。通过对态密度和能带结构的分析，我们发现，无论有无空位，石墨烯在异质结构中都保留了狄拉克锥，而不含空位和含有VO单空位的异质结构中的1T−MnO₂单层表现出半金属和磁性行为。这些性质主要来自3d−Mn和2p−O态的杂化。在这两种情况下，异质结构都具有3.00 μβ/Mn的磁矩。由此行为可以推断，含和不含VO单空位的异质结构都可用于自旋电子学。
