[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"doc-detail-121491-en":3,"doc-seo-121491-105":30,"detail-sidebar-cat-0-en-105":91},{"code":4,"msg":5,"data":6},0,"success",{"doc_id":7,"user_id":8,"nickname":9,"user_avatar":10,"doc_module":4,"category_id":11,"category_name":12,"doc_title":13,"doc_description":14,"doc_content":15,"file_id":16,"file_url":17,"file_type":18,"file_size":19,"view_count":20,"is_deleted":4,"is_public":20,"is_downloadable":20,"audit_status":20,"page_count":21,"language":22,"language_code":23,"site_id":24,"html_lang":23,"table_of_contents":25,"faqs":26,"seo_title":27,"seo_description":14,"update_tm":28,"read_time":29},121491,1374391974564,"Clementine","https://ap-avatar.wpscdn.com/avatar/14000253aa45c000a9e?x-image-process=image/resize,m_fixed,w_180,h_180&k=1779874745381141002",8,"Research & Report","Chasing Anharmonicities in Polarization-Orientation Raman Spectra of Acene Crystals with Machine Learning","We present a first-principles machine-learning computational framework to investigate anharmonic effects in polarization-orientation (PO) Raman spectra of molecular crystals, focusing on anthracene and naphthalene. The method combines ML models for interatomic potentials and polarizability tensors to enable efficient, large-scale simulations capturing temperature-dependent vibrational dynamics beyond the harmonic approximation. It reproduces qualitative experimental features and identifies signatures of anharmonic lattice dynamics, thermal expansion, and Raman tensor symmetries, while showing only subtle deviations from quasi-harmonic predictions for polarization dependence.","arXiv :2510 .04843v1 [ cond-mat .mtrl-sci ] 6 Oct 2025  \nChasing Anharmonicities in Polarization-Orientation Raman Spectra of Acene  \nCrystals with Machine Learning  \nPaolo Lazzaroni, Shubham Sharma, and Mariana Rossi∗  \nMPI for the Structure and Dynamics of Matter,  \nLuruper Chaussee 149, 22761 Hamburg, Germany  \n(Dated: October 7, 2025)  \nWe present a first-principles machine-learning computational framework to investigate anharmonic effects in polarization-orientation (PO) Raman spectra of molecular crystals, focusing on anthracene and naphthalene. By combining machine learning models for interatomic potentialsand polarizability tensors, we enable efficient, large-scale simulations that capture temperaturedependent vibrational dynamics beyond the harmonic approximation. Our approach reproduces key qualitative features observed experimentally. We show, systematically, what are the fingerprints of anharmonic lattice dynamics, thermal expansion, and Raman tensor symmetries on PO-Raman intensities. However, we find that the simulated polarization dependence of Raman intensities shows only subtle deviations from quasi-harmonic predictions, failing to capture the pronounced temperature-dependent changes that have been reported experimentally in anthracene. We propose that part of these inconsistencies stem from the impossibility to deconvolute certain vibrational peaks when only experimental data is available. This work therefore provides a foundation to improve the interpretation of PO-Raman experiments in complex molecular crystals with the aid of theoretical simulations.  \nI. INTRODUCTION  \nMolecular crystals are a class of solids where the molecular units, which constitute the basis of the crystal lattice, are kept together by intermolecular (non-covalent) interactions. The weak nature of these forces, when compared to those responsible in covalent bonds, allows one to identify two distinct energy scales in the nuclear lattice dynamics. At higher energies, intramolecular vibrations usually give rise to phonon branches with flat dispersion, as a result of the weakly perturbed internal motion of the individual molecules. In contrast, at low energies, the collective translations and hindered rotations of the molecular units are responsible for the unique spectral fingerprints of a given crystal structure.  \nThese low-frequency modes, typically below 200 cm −1 , dictate numerous properties of organic molecular crystals. It has been discussed, for example, how this region determines polymorph ordering at finite temperatures, by strongly contributing to the vibrational free energy [1–3], or how it dominates heat [4, 5] and charge [6, 7] carrier mobility in organic semiconductors. Because the weak intermolecular interactions lead to large-amplitude motion, these collective lattice vibrations can exhibit pronounced anharmonic character. Taking into account deviations from the ideal harmonic crystal picture is especially relevant when modeling these systems.  \nRecently, it was shown [8, 9] that polarizationorientation (PO) vibrational Raman scattering experiments conducted on several molecular crystals, including some linear oligoacenes, reveal an effect that has been attributed to anharmonic coupling between low-frequency intermolecular phonon modes. This effect consists of a  \n∗ [mariana.rossi@mpsd.mpg.de](mariana.rossi@mpsd.mpg.de)  \ndeviation of the polarization dependence of the Raman intensity of some phonon modes from the prediction of the harmonic crystal approximation. To rationalize this finding, a two-mode model, allowing phonon-phonon coupling in the description of inelastic light scattering, was presented in Ref. [10] . Parameters that were fitted on this model, based on the experimental data, could successfully explain the pattern that was measured and led to the conclusion that anharmonic mode-coupling terms are necessary for a complete description of the Raman scattering process in molecular crystals.  \nIn this paper, we provide an","cbCaic1RFhqBngbX","https://ap.wps.com/l/cbCaic1RFhqBngbX","pdf",7275434,1,36,"English","en",105,"# Introduction\n## Molecular crystals and vibrational energy scales\n## Anharmonic effects in PO-Raman experiments\n## Raman-scattering framework and anharmonic treatments\n## Machine-learning models and benchmarking","[{\"question\":\"What is the goal of the proposed framework for PO-Raman spectra?\",\"answer\":\"The framework aims to reproduce, explain, and provide quantitative insights into anharmonic effects directly probed by polarization-orientation Raman spectroscopy in molecular crystals.\"},{\"question\":\"Which materials are studied as case examples?\",\"answer\":\"The study focuses on linear oligoacene molecular crystals, particularly naphthalene and anthracene.\"},{\"question\":\"How do the simulations relate to the harmonic or quasi-harmonic predictions?\",\"answer\":\"The approach reproduces qualitative experimental features and identifies signatures of anharmonic lattice dynamics, but the simulated polarization dependence shows only subtle deviations from quasi-harmonic predictions, missing pronounced temperature-dependent changes reported experimentally.\"}]","Chasing Anharmonicities in Polarization-Orientation Raman Spectra of Acene Crystals with Machine Learning | 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is the goal of the proposed framework for PO-Raman spectra?","Question",{"text":75,"@type":76},"The framework aims to reproduce, explain, and provide quantitative insights into anharmonic effects directly probed by polarization-orientation Raman spectroscopy in molecular crystals.","Answer",{"name":78,"@type":73,"acceptedAnswer":79},"Which materials are studied as case examples?",{"text":80,"@type":76},"The study focuses on linear oligoacene molecular crystals, particularly naphthalene and anthracene.",{"name":82,"@type":73,"acceptedAnswer":83},"How do the simulations relate to the harmonic or quasi-harmonic predictions?",{"text":84,"@type":76},"The approach reproduces qualitative experimental features and identifies signatures of anharmonic lattice dynamics, but the simulated polarization dependence shows only subtle deviations from quasi-harmonic predictions, missing pronounced temperature-dependent changes reported 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