The widely used crystal structures for both heptazine-based and triazine-based two-dimensional (2D) graphitic carbon nitride (g-C₃N₄) are the flat P-6m2 configurations. However, the experimentally synthesized 2D g-C₃N₄ possess thickness ranging in 0.2–0.5 nm, indicating that the theoretically used flat P-6m2 configurations are not the correct ground states. In this work, we propose three new corrugated structures P321, P3m1 and Pca21 with energies of 66 (86), 77 (87) and 78 (89) meV/atom lower than that of the corresponding heptazine-based (triazine-based) g-C₃N₄ in flat P-6m2 configuration, respectively. These corrugated structures have very similar periodic patterns to the flat P-6m2 ones and they are difficult to be distinguished from each other according to their top-views. The optimized thicknesses of the three corrugated structures ranging in 1.347–3.142 Å are in good agreement with the experimental results. The first-principles results show that these corrugated structural candidates are also semiconductors with band gaps larger than those of the correspondingly flat P-6m2 ones. Furthermore, they possess also suitable band edge positions for sun-light-driven water-splitting at both pH = 0 and pH = 7 environments. Our results show that these three new structures are more promising candidates for the experimentally synthesized g-C₃N₄.

庚嗪基和三嗪基二维（2D）石墨碳氮化物（gC ₃ N ₄）广泛使用的晶体结构是平面P-6m2构型。但是，实验合成的2D gC ₃ N ₄的厚度在0.2-0.5 nm之间，这表明理论上使用的平面P-6m2配置不是正确的基态。在这项工作中，我们提出了三种新的瓦楞结构P321，P3m1和Pca21，其能量分别为66（86），77（87）和78（89）meV /原子，比相应的庚嗪基（三嗪基）gC低₃ N ₄分别在P-6m2平面配置中。这些波纹状结构的周期性图案与平坦的P-6m2极为相似，很难根据其俯视图将它们区分开。三种波纹结构的最佳厚度在1.347-3.142Å之间，与实验结果吻合良好。第一性原理结果表明，这些波纹状的候选结构也是带隙大于相应的平坦P-6m2的带隙的半导体。此外，它们还具有适合在pH = 0和pH = 7的环境下进行阳光驱动的水分解的条带边缘位置。我们的结果表明，这三个新结构是实验合成gC ₃ N _4的更有希望的候选者。