Despite the wide availability of density functional theory (DFT) codes, their adoption by the broader materials science community remains limited due to challenges such as software installation, input preparation, high-performance computing setup, and output analysis. To overcome these barriers, we introduce the Quantum ESPRESSO app, an intuitive, web-based platform built on AiiDAlab that integrates user-friendly graphical interfaces with automated DFT workflows. The app employs a modular Input-Process-Output model and a plugin-based architecture, providing predefined computational protocols, automated error handling, and interactive results visualization. We demonstrate the app's capabilities through plugins for electronic band structures, projected density of states, phonon, infrared/Raman, X-ray and muon spectroscopies, Hubbard parameters (DFT+U+V), Wannier functions, and post-processing tools. By extending the FAIR principles to simulations, workflows, and analyses, the app enhances the accessibility and reproducibility of advanced DFT calculations and provides a general template to interface with other first-principles calculation codes.

X-ray Photoelectron Spectroscopy (XPS) is a powerful technique to probe chemical states and interfacial processes in battery materials, but a quantitative interpretation is often hindered by the complex, heterogeneous microstructures that form during operation and dominate electrochemical cycling. Silicon based anodes represent a paradigmatic example in Li batteries, as (de)lithiation proceeds through the formation of strongly disordered Li_xSi phases and crystal-amorphous transformations that are hard to characterize. Here, we introduce a computational framework that combines machine-learning (ML) prediction of core-level binding energies to large-scale atomistic simulations – Grand Canonical Monte Carlo (GCMC) complemented with molecular dynamics (MD), driven by a ML potential – for a systematic sampling of lithiation states and local atomic environments. This approach yields stoichiometry maps that match the characteristic experimental trends observed in operando and ex situ XPS measurements, including the distinctive Si 2p spectroscopic signatures associated with the crystal-to-amorphous disordering driving early delithiation.

Van der Waals 2D crystals, with their dangling bond-free surfaces and extremely low roughness levels, are highly appealing substrates for the epitaxial growth of organic semiconductors. The growth has important consequences in the fabrication of organic electronic components such as organic light diodes. Here, using a MoS2 nanosheet, an n-type semiconducting 2D material, as a substrate, we grow highly ordered crystalline needles made of sexithiophene (T6), a p-type organic semiconductor. Using atomic force microscopy topographic analysis, X-ray diffraction, and micro-Raman spectroscopy, we show that the T6 needles show both short- and long-range order thanks to an alignment between the T6 long axis and high symmetry directions in MoS2. By statistical analysis we demonstrate that the T6 needles show a small mismatch of ±7° between their long axis and the zigzag directions of MoS2. Interestingly, T6 grown on multilayer graphene does not show such an order, resulting in a randomly oriented needle network, while T6 grown on atomically thin MoS2 still show long-range order. Density functional theory predicts an alignment of the T6 long axis along the zigzag direction of MoS2 to minimize the total energy of the system by maximizing the number of thiophene rings positioned on top of sulfur atoms from MoS2. The ideal interface between T6 molecules and MoS2 also has implications in the charge transfer of photoexcited carriers as demonstrated by microphotoluminescence spectroscopy. These results demonstrate that van der Waals materials are ideal substrates for the growth of organic molecules and that subtle variations in the van der Waals long-range potential can influence the long-range order of the molecular crystals. The ordered one-dimensional T6 crystallites are interesting for polarized or anisotropic optoelectronic applications.

Graphite, with its van der Waals layered structure, can accommodate a diverse array of intercalant species within its layers. Alkali metals (AMs), a family of donor intercalants, play a pivotal role in technological advancements, notably in lithium-ion batteries. Owing to its structural simplicity and the feasibility of producing high-quality single crystals spanning areas up to hundreds of micrometers squared, few-layer (FL) graphene serves as an exemplary system for investigating the dynamics of AM adsorption and intercalation. This study focuses on the deposition of potassium atoms in ultra-high vacuum onto mechanically exfoliated four- to five-layer FL and multilayer (ML) graphene. Employing spatially resolved Raman spectroscopy, we examine the impact of potassium adsorption, diffusion, and intercalation. Our findings reveal intricate potassium intake spatial patterns in FL graphene. The distinct spatial inhomogeneities of FL graphene are not observed in ML graphene. Density functional theory calculations also confirmed a complex scenario where both charging and steric hindrance introduce local strain in the graphene layers. Furthermore, charge donation from potassium atoms both to adjacent graphene layers and to more distant layers not adjacent to potassium atoms suggest a modification of the structural and vibrational properties of graphene consistent with the Raman experiments. The detection of intercalation fronts and domains with constant charging, and thus constant potassium densities, underscores the complex and collective nature of the potassium diffusion and intercalation in FL graphene, offering valuable insights for potential applications in energy storage systems.

During the first charge-discharge cycle, silicon-based batteries show an important capacity loss not only due to the formation of the solid electrolyte interphase (SEI) but also other effects taking place during the expansion-contraction sequence upon (de)alloying, such as electrochemical reduction of native oxide, Li trapping, and loss of active material. To understand this first-cycle irreversibility, quantitative methods are needed to characterize the chemical environment of silicon and lithium in the bulk of the cycled electrodes. Here, a methodology based on multiedge X-ray Raman scattering is reported, as applied to model silicon electrodes prepared in fully lithiated and delithiated states after the first cycle. The spectra are recorded at the C, O, F, and Li K-edges, as well as Si L2,3 edge, and are analyzed using linear combinations of both experimental and computed reference spectra. Prototypical SEI compounds such as Li2CO3, LiF, and LiPF6, as well as electrode constituents such as binder and conductive carbon, crystalline Si, native SiO2, and Li x Si phases (x being the lithiation index) are taken into account to identify the main species, isolate their relative contributions, and quantitatively evaluate the proportions of organic and inorganic products. This analysis shows that 35% of the carbonates formed in the SEI during the lithiation are dissolved upon delithiation and that part of the Li x Si alloys remains present after delithiation. Moreover, in combination with electrochemical data, it enables the quantification of the lithium lost in the first cycle, 17% of which is trapped in disconnected silicon particles, while 30% forms a fluorine-rich stable SEI and 53% a carbonate-rich partially dissolvable SEI. These results pave the way to systematic, reference data-informed and modeling-assisted studies of SEI characteristics in the bulk of electrodes prepared under controlled state-of-charge and state-of-health conditions.

Doping of semiconductor nanocrystals is a well-established process to impart new or enhanced functionalities to the host material. In this work we present the synthesis of colloidal WO3 nanocrystals doped with interstitial methylammonium cations. The organic cations are located within the voids of the WO3 cage and increase the charge carrier concentration. As a result, the nanocrystals exhibit intense surface plasmon resonances in the near infrared, comparable to those obtained for WO3 “bronzes” doped with alkali metals. We confirm the successful incorporation of these novel organic dopants through a combined experimental and theoretical study. Furthermore, we demonstrate the ability to dope the nanocrystals with even larger cations including formamidinium, providing a pathway to obtaining WO3 doped with bespoke organic cations that offer additional functionalities for use in optics, electronics and catalysis.

Helically coiled, semiconducting graphenic nanostructures show exceptional promise for nanoelectronics, yet their synthesis has remained challenging due to their inherently strained backbone and the difficulties associated with structural characterization. In this work, we demonstrate the synthesis and characterization of laterally π-extended polyhelicenes (EPHs), achieved through regioselective cyclodehydrogenation. Spectroscopic and microscopic analyses, including mass spectrometry, solid-state NMR, scanning-probe microscopy, and transmission electron microscopy, confirm the well-defined helical, layered architecture of the EPHs. Ultrafast terahertz spectroscopy reveals pronounced intrahelix photoconductivity, demonstrating their potential as carbon-based nanoscale conductors. The scalable synthetic approach described in this work unlocks the application potential of carbon-based helical nanostructures, paving the way for nanoinductors in nanoscale solenoids, spin-selective electronics, and future high-frequency nanoelectronic devices.

Internal conversion (IC) is a common radiationless transition in polyatomic molecules. Theory predicts that molecular vibrations assist IC between excited states, and ultrafast experiments can provide insight into their structure-function relationship. Here we elucidate the dynamics of the vibrational modes driving the IC process within the Q band of a functionalized porphyrin molecule. Through a combination of ultrafast multidimensional spectroscopies and theoretical modeling, we observe a 60 fs Q(y)-Q(x) IC and demonstrate that it is driven by the interplay among multiple high-frequency modes. Notably, we identify 1510 cm(-1) as the leading tuning mode that brings the porphyrin to an optimal geometry for energy surface crossing. By employing coherent wave packet analysis, we highlight a set of short-lived vibrations (1200-1400 cm(-1)), promoting the IC within approximate to 60 fs. Furthermore, we identify one coupling mode (1350 cm(-1)) that is responsible for vibronic mixing within the Q states. Our findings indicate that porphyrin-core functionalization modulates IC effectively, offering new opportunities in photocatalysis and optoelectronics.

We analyze the internal conversion dynamics within the Qy and Qx excited states of both bare and functionalized porphyrins, which are known to exhibit significantly different time constants experimentally. Through the integration of two complementary approaches, static calculation of per-mode reorganization energies and nonadiabatic molecular dynamics, we achieve a comprehensive understanding of the factors determining the different behavior of the two molecules. We identify the key normal and essential modes responsible for the population transfer between excited states and discuss the efficacy of different statistical and nonstatistical analyses in providing a full physics-based description of the phenomenon.

The intricate relationship between local atomic arrangements and electronic states significantly influences the electrochemical properties of Li-ion battery cathode materials. Despite decades of investigation, a consensus regarding the local atomic and electronic structure of LiNiO2 remains elusive. This ambiguity stems from the potential distortion of Ni sites, either via Jahn-Teller (JT) distortion or bond disproportionation (BD), complicating the understanding of the charge compensation mechanism involving Ni and O. This study compares the structures of LiNiO2 and NaNiO2, a JT system, using an innovative approach that integrates bulk spectroscopy techniques on standardized interoperable samples for enhanced reliability. While X-r and theoretical calculations fail to differentiate between the proposed scenarios, Raman spectroscopy highlights local structural distinctions between monoclinic NaNiO2 and rhombohedral LiNiO2. HAXPES confirms various formal oxidation states for Ni, supported by RIXS data indicating 3d8 states, emphasizing negative charge transfer from Ni and some bond disproportionation in LiNiO2. Regarding charge compensation, XRS and RIXS suggest oxygen hole involvement in redox activity, whereas Raman spectroscopy does not detect molecular oxygen. This comprehensive spectroscopic analysis highlights the importance of correlative characterization workflows in elucidating complex structural-electrochemical relationships.

The intimate correlation between the local atomic arrangement and electronic states in Li-ion battery cathode materials plays a crucial role in determining their electrochemical properties, including capacity, cycling stability, and rate capability. Despite almost 30 years of research efforts on high performance cathodes based on Ni rich layered oxides, there is still no consensus on LiNiO2 local atomic and electronic structure. Ni sites could be either Jahn-Teller distorted or bond disproportionated and the role of Ni and oxygen in the charge compensation mechanism remains unclear. In this study, we compare the local and electronic structure of LiNiO2 and NaNiO2, a long-range Jahn-Teller system, using a novel approach which aims at correlating the results from bulk spectroscopy techniques, particularly under operando conditions, obtained on standard samples to ensure sample interoperability and enhance the reliability and robustness of our results. Despite being a site-selective and local technique, XAS is unable to discriminate between the proposed scenarios, as confirmed also by theoretical calculations. On the contrary, Raman spectroscopy show local structural differences between monoclinic distorted NaNiO2 and rhombohedral LiNiO2. Additionally, HAXPES confirms the presence of multiple formal oxidation states for Ni, and RIXS data provides evidence of 3d8 states, confirming the negative charge transfer character of Ni and some degree of bond disproportionation in LiNiO2. Regarding the charge compensation mechanism, XRS and RIXS support the participation of oxygen holes in the redox activity, while Raman spectroscopy does not detect molecular oxygen. By combing several high-fidelity spectroscopy datasets, this study shows the value of correlative characterization workflows to provide insights into complex structural-electrochemical relationships.

Discerning the impact of the coherent motion of the nuclei on the timing and efficiency of charge transfer at the donor-acceptor interface is essential for designing performance-enhanced optoelectronic devices. Here, we employ an experimental approach using photocurrent detection in coherent multidimensional spectroscopy to excite a donor aromatic macrocycle and collect the charge transferred to a 2D acceptor layer. For this purpose, we prepared a cobalt phthalocyanine-graphene (CoPc-Gr) interface. Unlike blends, the well-ordered architecture achieved through the physical separation of the two layers allows us to unambiguously collect the electrical signal from graphene alone and associate it with a microscopic understanding of the whole process. The CoPc-Gr interface exhibits an ultrafast electron-transfer signal, stemming from an interlayer mechanism. Remarkably, the signal presents an oscillating time evolution modulated by coherent vibrations originating from the laser-excited CoPc states. By performing Fourier analysis on the beatings and correlating it with the Raman features, along with a comprehensive first-principles characterization of the vibrational coupling in the CoPc excited states, we successfully identify both the orbitals and molecular vibrations that promote the charge transfer at the interface.

Silicon nanoparticles (c-Si NPs) are considered promising candidates for the active material in Si-based anodes, offering high gravimetric capacity and helping to mitigate volume expansion effects. However, the formation of an unstable Solid Electrolyte Interphase (SEI) around the nanoparticles leads to increased irreversible lithium consumption, resulting in reduced capacity and poor cycling stability. In this context, core-level spectroscopies are established techniques to assess the evolution and composition of the SEI. While X-ray spectroscopies provide valuable insights into atomic and electronic structures, interpreting them in complex systems could be challenging, highlighting the need of theoretical insights from ab-initio approaches. Our study focuses on the changes occurring in c-Si NPs and the SEI during the initial charge cycle, leveraging post-mortem core-level spectra at various states of charge (SOC). We employ a multi-edge analysis coupled with a fitting approach based on known experimental references and theoretical simulations. Additionally, we demonstrate how comparing experimental spectra with theoretical references allows tracking changes at the NP level, including amorphization and surface oxidation. Finally, we discuss some of the limitations of our theoretical description and propose addressing them through machine learning approaches. This work is supported by the European Union’s Horizon 2020 research and innovation program (BIG-MAP, Grant No. 957189, also part of the BATTERY 2030+ initiative, Grant No. 957213).

The automation of ab initio simulations is essential in view of performing high-throughput (HT) computational screenings oriented to the discovery of novel materials with desired physical properties. In this work, we propose algorithms and implementations that are relevant to extend this approach beyond density functional theory (DFT), in order to automate many-body perturbation theory (MBPT) calculations. Notably, an algorithm pursuing the goal of an efficient and robust convergence procedure for GW and BSE simulations is provided, together with its implementation in a fully automated framework. This is accompanied by an automatic GW band interpolation scheme based on maximally localized Wannier functions, aiming at a reduction of the computational burden of quasiparticle band structures while preserving high accuracy. The proposed developments are validated on a set of representative semiconductor and metallic systems.

Molecular motors have chemical properties that enable unidirectional motion, thus breaking microscopic reversibility. They are well studied in solution, but much less is known regarding their behavior on solid surfaces. Here, single motor molecules adsorbed on a Cu(111) surface are excited by voltages pulses from an STM tip, which leads to their rotation around a fixed pivot point. Comparison with calculations shows that this axis results from a chemical bond of a sulfur atom in the chemical structure and a metal atom of the surface. While statistics show approximately equal rotations in both directions, clockwise and anticlockwise, a detailed study reveals that these motions are enantiomer-specific. Hence, the rotation direction of each individual molecule depends on its chirality, which can be determined from STM images. At first glance, these dynamics could be assigned to the activation of the motor molecule, but our results show that this is unlikely as the molecule remains in the same conformation after rotation. Additionally, a control molecule, although it lacks unidirectional rotation in solution, also shows unidirectional rotation for each enantiomer. Hence, it seems that the unidirectional rotation is not specifically related to the motor property of the molecule. The calculated energy barriers for motion show that the propeller-like motor activity requires higher energy than the simple rotation of the molecule as a rigid object, which is therefore preferred.

The conversion of semimetallic suspended graphene (Gr) to a large-gap semiconducting phase is here realized by controlled adsorption of atomic hydrogen (deuterium) on free-standing nanoporous Gr veils. This approach allows to achieve a very clean and neat adsorption, overcoming any spurious influence associated to the presence of substrates. The effects of local rehybridization from sp(2) to sp(3) chemical bonding are investigated by combining X-ray photoelectron spectroscopy and high-resolution electron energy-loss spectroscopy (HREELS) with ab-initio based modelling. We find that the hydrogen adatoms on the C sites induce a stretching frequency, clearly iden-tified in the vibrational spectra thanks to the use of the D isotope. Overall, the results are compatible with the predicted fingerprints of adsorption on both sides of Gr corresponding to the graphane configuration. Moreover, HREELS of the deuterated samples shows a sizeable opening of the optical band gap, i.e. 3.25 eV, consistent with the modified spectral density observed in the valence band photoemission. The results are in agreement with ab-initio calculations by GW and Bethe-Salpeter equation approaches, predicting a large quasiparticle gap opening and huge exciton binding energy.

We systematically applied excited-state normal mode analysis to investigate and compare the relaxation and internal conversion dynamics of a free-base porphyrin (BP) with those of a novel functional porphyrin (FP) derivative. We discuss the strengths and limitations of this method and employ it to predict very different dynamical behaviors of the two compounds and to clarify the role of high reorganization energy modes in driving the system toward critical regions of the potential energy landscape. We identify the modes of vibrations along which the energy gap between two excited-state potential energy surfaces within the Q band manifold may vanish and find that the excess energy to reach this "touching" region is significantly reduced in the case of FP (0.16 eV) as compared to the one calculated for BP (0.92 eV). Our findings establish a link between the chemical functionalization and the electronic and vibrational structure that can be exploited to control the internal conversion pathways in a systematic way.

Multidimensional spectroscopies unveil the presence of vibronic coupling within the Q-states in a free-base porphyrin. High-frequency coupling and tuning modes drive the ultrafast internal conversion and track the excited state structural evolution.

Conversion of free-standing graphene into pure graphane─where each C atom is sp3 bound to a hydrogen atom─has not been achieved so far, in spite of numerous experimental attempts. Here, we obtain an unprecedented level of hydrogenation (≈90% of sp3 bonds) by exposing fully free-standing nanoporous samples─constituted by a single to a few veils of smoothly rippled graphene─to atomic hydrogen in ultrahigh vacuum. Such a controlled hydrogenation of high-quality and high-specific-area samples converts the original conductive graphene into a wide gap semiconductor, with the valence band maximum (VBM) ∼ 3.5 eV below the Fermi level, as monitored by photoemission spectromicroscopy and confirmed by theoretical predictions. In fact, the calculated band structure unequivocally identifies the achievement of a stable, double-sided fully hydrogenated configuration, with gap opening and no trace of π states, in excellent agreement with the experimental results.

Graphene nanoribbons functionalized with methoxy groups were synthesized. Theoretical studies predicted reduced bandgap and effective mass of charge carriers. THz spectroscopy revealed ∼25% enhancement of the photoconductivity.