Hexagonal boron nitride (h-BN) and semiconducting transition metal dichalcogenides (TMDs) promise greatly improved electrostatic control in future scaled electronic devices. To quantify the prospects of these materials in devices, we calculate the out-of-plane and in-plane dielectric constant from first principles for TMDs in trigonal prismatic and octahedral coordination, as well as for h-BN, with a thickness ranging from monolayer and bilayer to bulk. Both the ionic and electronic contribution to the dielectric response are computed. Our calculations show that the out-of-plane dielectric response for the transition-metal dichalcogenides is dominated by its electronic component and that the dielectric constant increases with increasing chalcogen atomic number. Overall, the out-of-plane dielectric constant of the TMDs and h-BN increases by around 15% as the number of layers is increased from monolayer to bulk, while the in-plane component remains unchanged. Our computations also reveal that for octahedrally coordinated TMDs the ionic (static) contribution to the dielectric response is very high (4.5 times the electronic contribution) in the in-plane direction. This indicates that semiconducting TMDs in the tetragonal phase will suffer from excessive polar-optical scattering thereby deteriorating their electronic transport properties.

六方氮化硼（h-BN）和半导体过渡金属二卤化碳（TMDs）有望在未来的规模化电子设备中极大地改善静电控制。为了量化这些材料在器件中的应用前景，我们根据三棱柱和八面体配位的TMD以及h-BN的第一原理计算面外和面内介电常数，厚度范围为单层和双层散装。计算离子和电子对介电响应的贡献。我们的计算表明，过渡金属二卤化物的面外介电响应受其电子成分支配，并且介电常数随硫族元素原子数的增加而增加。全面的，随着层数从单层增加到整体，TMD和h-BN的面外介电常数增加约15％，而面内分量保持不变。我们的计算还显示，对于八面体配位的TMD，离子（静电）对介电响应的贡献在平面内方向上非常高（是电子贡献的4.5倍）。这表明在四方相中的半导体TMD将遭受过度的极光散射，从而使它们的电子传输性能恶化。平面方向的电子贡献的5倍）。这表明在四方相中的半导体TMD将遭受过度的极光散射，从而使它们的电子传输性能恶化。平面方向的电子贡献的5倍）。这表明在四方相中的半导体TMD将遭受过度的极光散射，从而使它们的电子传输性能恶化。