The paper by A. Molina-Sánchez and L. Wirtz investigates the phonon dispersion relations of single-layer and bulk dichalcogenides MoS₂ and WS₂ using *ab initio* calculations. The authors focus on the behavior of Raman-active modes $A_{1g}$ and $E_{2g}^1$ as the number of layers changes. They find that the $A_{1g}$ mode increases in frequency with more layers, while the $E_{2g}^1$ mode decreases, which contradicts the expectation based on weak interlayer interactions. This decrease in the $E_{2g}^1$ mode is attributed to the enhanced dielectric screening of the long-range Coulomb interaction, which overcompensates for the increased short-range interaction due to weak interlayer forces. The study also provides a detailed analysis of the atomic force constants, separating the short-range and long-range contributions to the interatomic forces. The results are compared with experimental data, showing good agreement. The findings are relevant for understanding the vibrational properties of these materials and their potential applications in optoelectronic devices.The paper by A. Molina-Sánchez and L. Wirtz investigates the phonon dispersion relations of single-layer and bulk dichalcogenides MoS₂ and WS₂ using *ab initio* calculations. The authors focus on the behavior of Raman-active modes $A_{1g}$ and $E_{2g}^1$ as the number of layers changes. They find that the $A_{1g}$ mode increases in frequency with more layers, while the $E_{2g}^1$ mode decreases, which contradicts the expectation based on weak interlayer interactions. This decrease in the $E_{2g}^1$ mode is attributed to the enhanced dielectric screening of the long-range Coulomb interaction, which overcompensates for the increased short-range interaction due to weak interlayer forces. The study also provides a detailed analysis of the atomic force constants, separating the short-range and long-range contributions to the interatomic forces. The results are compared with experimental data, showing good agreement. The findings are relevant for understanding the vibrational properties of these materials and their potential applications in optoelectronic devices.