Large excitonic binding energies in monolayers of transition metal dichalcogenides such as molybdenum disulfide (MoS₂), molybdenum diselenide (MoSe₂), tungsten disulfide (WS₂) and tungsten diselenide (WSe₂), were calculated using a gravitational search algorithm. The optimized fitness function is based on a two dimensional (2D) effective mass model of excitons, parameterized by first principle calculations, including a suitable treatment of screening. In addition to the ground state, the binding energies of the first few excited states of the exciton were computed, hence the optical transition energies, as a function of principal quantum number n, were obtained for the exciton states. The method was also used to predict the corresponding 2D polarizabilities, and consequently, dielectric constants for the 2D semiconductors. Dependence of the effective dielectric constants on n was also investigated. Our results compare favorably with existing theoretical methods based on density function theory or GW approximation and the Bethe–Salpeter equation. Furthermore, our results are in reasonable agreement with recent experimental measurements.

使用重力搜索算法计算了过渡金属二硫化碳（如二硫化钼（MoS ₂），二硒化钼（MoSe ₂），二硫化钨（WS ₂）和二硒化钨（WSe ₂））单层中的大激子结合能。优化的适应度函数基于激子的二维（2D）有效质量模型，该模型通过第一原理计算（包括适当的筛选处理）进行参数化。除了基态之外，还计算了激子的前几个激发态的结合能，因此，光学跃迁能与主量子数n的关系为：是针对激子态而获得的。该方法还用于预测相应的2D极化率，并因此预测2D半导体的介电常数。还研究了有效介电常数对n的依赖性。我们的结果与现有的基于密度函数理论或GW近似和Bethe–Salpeter方程的理论方法相比具有优势。此外，我们的结果与最近的实验测量结果基本吻合。