Infrared and Raman spectroscopies are ubiquitous techniques employed in many experimental laboratories, thanks to their fast and non-destructive nature able to capture materials’ features as spectroscopic fingerprints. Nevertheless, these measurements frequently need theoretical and computational support in order to unambiguously decipher and assign complex spectra. Linear-response theory provides an effective way to obtain the higher-order derivatives needed, but its applicability to modern exchange-correlation functionals and pseudopotential formalism remains limited. Here, we devise an automated, open-source, user-friendly approach based on density-functional theory and the electric-enthalpy functional to allow seamless calculation from first principles of infrared absorption and reflectivity, together with zone-center phonons, static dielectric tensor, and Raman spectra. By employing a finite-displacement and finite-field approach, we allow for the use of any functional, as well as an efficient treatment of large low-symmetry structures. Additionally, we propose a simple scheme for efficiently sampling the Brillouin zone at different electric fields. To demonstrate the capabilities of the present approach, we study ferroelectric LiNbO₃ crystal as a paradigmatic example, and predict infrared and Raman spectra using various (semi)local, Hubbard corrected, and hybrid functionals. Our results also show how PBE0 and extended Hubbard functionals (PBEsol+U+V) yield for this case the best match in term of peak positions and intensities, respectively.

红外和拉曼光谱是许多实验实验室普遍采用的技术，因为它们具有快速和非破坏性的性质，能够捕获材料的特征作为光谱指纹。然而，这些测量经常需要理论和计算支持，以便明确地破译和分配复杂的光谱。线性响应理论提供了一种获得所需高阶导数的有效方法，但其对现代交换相关泛函和赝势形式主义的适用性仍然有限。在这里，我们设计了一种基于密度泛函理论和电焓泛函的自动化、开源、用户友好的方法，可以根据红外吸收和反射率的第一原理以及区域中心声子、静态介电张量进行无缝计算和拉曼光谱。通过采用有限位移和有限场方法，我们允许使用任何泛函，以及对大型低对称结构的有效处理。此外，我们提出了一种简单的方案，可以在不同电场下对布里渊区进行有效采样。为了证明本方法的功能，我们以铁电 LiNbO ₃晶体作为范例进行研究，并使用各种（半）局部、哈伯德校正和混合泛函来预测红外和拉曼光谱。我们的结果还显示了 PBE0 和扩展哈伯德泛函 (PBEsol+U+V) 在这种情况下如何分别在峰值位置和强度方面产生最佳匹配。