QuantumATK: An integrated platform of electronic and atomic-scale modelling tools

QuantumATK is an integrated set of atomic-scale modelling tools developed since 2003 by professional software engineers in collaboration with academic researchers. While different aspects and individual modules of the platform have been previously presented, the purpose of this paper is to give a general overview of the platform. The QuantumATK simulation engines enable electronic-structure calculations using density functional theory or tight-binding model Hamiltonians, and also offers bonded or reactive empirical force fields in many different parametrizations. Density functional theory is implemented using either a plane-wave basis or expansion of electronic states in a linear combination of atomic orbitals. The platform includes a long list of advanced modules, including Green's-function methods for electron transport simulations and surface calculations, first-principles electron-phonon and electron-photon couplings, simulation of atomic-scale heat transport, ion dynamics, spintronics, optical properties of materials, static polarization, and more. Seamless integration of the different simulation engines into a common platform allows for easy combination of different simulation methods into complex workflows. Besides giving a general overview and presenting a number of implementation details not previously published, we also present four different application examples. These are calculations of the phonon-limited mobility of Cu, Ag and Au, electron transport in a gated 2D device, multi-model simulation of lithium ion drift through a battery cathode in an external electric field, and electronic-structure calculations of the composition-dependent band gap of SiGe alloys.Comment: Submitted to Journal of Physics: Condensed Matte

Dupilumab in the treatment of severe uncontrolled chronic rhinosinusitis with nasal polyps (CRSwNP): A multicentric observational Phase IV real-life study (DUPIREAL)

Background Chronic rhinosinusitis with nasal polyps (CRSwNP) is associated with significant morbidity and reduced health-related quality of life. Findings from clinical trials have demonstrated the effectiveness of dupilumab in CRSwNP, although real-world evidence is still limited. Methods This Phase IV real-life, observational, multicenter study assessed the effectiveness and safety of dupilumab in patients with severe uncontrolled CRSwNP (n = 648) over the first year of treatment. We collected data at baseline and after 1, 3, 6, 9, and 12 months of follow-up. We focused on nasal polyps score (NPS), symptoms, and olfactory function. We stratified outcomes by comorbidities, previous surgery, and adherence to intranasal corticosteroids, and examined the success rates based on current guidelines, as well as potential predictors of response at each timepoint. Results We observed a significant decrease in NPS from a median value of 6 (IQR 5–6) at baseline to 1.0 (IQR 0.0–2.0) at 12 months (p < .001), and a significant decrease in Sino-Nasal Outcomes Test-22 (SNOT-22) from a median score of 58 (IQR 49–70) at baseline to 11 (IQR 6–21; p < .001) at 12 months. Sniffin' Sticks scores showed a significant increase over 12 months (p < .001) compared to baseline. The results were unaffected by concomitant diseases, number of previous surgeries, and adherence to topical steroids, except for minor differences in rapidity of action. An excellent-moderate response was observed in 96.9% of patients at 12 months based on EPOS 2020 criteria. Conclusions Our findings from this large-scale real-life study support the effectiveness of dupilumab as an add-on therapy in patients with severe uncontrolled CRSwNP in reducing polyp size and improving the quality of life, severity of symptoms, nasal congestion, and smell

Development of an atomistic/continous simulation tool for nanoelectronic devices

La simulazione dei moderni dispositivi elettronici è una grande sfida per la comunità ingegneristica. L'enorme progresso nei processi di fabbricazione ha permesso una riduzione della dimensione dei dispositivi talmente spinta che fenomeni tipici della scala di lunghezza nanometrica giocano un ruolo cruciale. Inoltre stiamo assistendo a un grande sforzo teso ad esplorare soluzioni tecnologiche alternatice ai tradizionali dispositivi a semiconduttore. Questo sforzo è rivolto verso la frontiera dell'elettronica molecolare, dei polimeri semiconduttori, delle strutture autoassemblanti, dei materiali quasi-unidimensionali e bidimensionali. In uno scenario simile è cruciale sviluppare strumenti di simulazione modulari, capaci di connettere modelli fisici differenti su scale geometriche differenti. Gli effetti quantistici giocano un ruolo fondamentale ed è necessario includere modelli che li descrivano, evitando però la tipica esplosione di complessità nell'implementazione di suddetti modelli. Per realizzare ciò è necessario andare verso un approccio multiscala, approccio già utilizzato con successo in meccanica statica. Lo scopo di questo lavoro è includere descrizioni e modelli atomistici in TiberCAD, un codice TCAD per la simulazione di dispositivi optoelettronici che può vantare eccellenti strumenti per interfacciare diversi modelli fisici in un ambiente multifisica/multiscala. I modelli atomistici inclusi sono utili al calcolo delle deformazioni elastiche, della geometria della struttura e degli stati elettronici. Infine, viene presentata anche una tecnica inedita per una descrizione quantistica efficiente del trasporto di carica. Questo lavoro vuole contrubuire a rendere TiberCAD uno strumento di riferimento per la simulazione di dispositivi optoelettronici su nanoscala.The simulation of novel optoelectronic devices is a great challenge for the engineering community. The enoromous progress in device fabrication technology allowed such a massive downscaling that geometrical feature in the nanoscale play a crucial role. Furthermore we have a great effort in exploring alternative solutions respect to more traditional semiconductor devices. It involves molecular electronic, semiconductive polymers, self-assembled structures, quasi-one dimensional and two dimensional materials. In such scenario it's crucial to develop modular simulation tools able to connect different physical models on different length scales. Quantum effect play an important role and we need to take them into account, avoiding anyway an explosion of the computational complexity. Thus it's needed to go in the direction of a multiscale approach, which is already applied with success in mechanical science. The goal of this work is to include atomistic description and atomistic models in TiberCAD, a Technology CAD code for simulation of optoelectronic devices which can rely on excellent instruments for interfacing different models in a multyphisics/multiscale environment. Atomistic models for the calculation of strain, structure geometry and electronic states have been included. A novel technique for describing quantum transport with an efficient algorithm is also presented. These work wants to push TiberCAD to be a reference tool for calculation of complex optoeletronic devices at the nanoscale

Development of an atomistic/continous simulation tool for nanoelectronic devices

La simulazione dei moderni dispositivi elettronici è una grande sfida per la comunità ingegneristica. L'enorme progresso nei processi di fabbricazione ha permesso una riduzione della dimensione dei dispositivi talmente spinta che fenomeni tipici della scala di lunghezza nanometrica giocano un ruolo cruciale. Inoltre stiamo assistendo a un grande sforzo teso ad esplorare soluzioni tecnologiche alternatice ai tradizionali dispositivi a semiconduttore. Questo sforzo è rivolto verso la frontiera dell'elettronica molecolare, dei polimeri semiconduttori, delle strutture autoassemblanti, dei materiali quasi-unidimensionali e bidimensionali. In uno scenario simile è cruciale sviluppare strumenti di simulazione modulari, capaci di connettere modelli fisici differenti su scale geometriche differenti. Gli effetti quantistici giocano un ruolo fondamentale ed è necessario includere modelli che li descrivano, evitando però la tipica esplosione di complessità nell'implementazione di suddetti modelli. Per realizzare ciò è necessario andare verso un approccio multiscala, approccio già utilizzato con successo in meccanica statica. Lo scopo di questo lavoro è includere descrizioni e modelli atomistici in TiberCAD, un codice TCAD per la simulazione di dispositivi optoelettronici che può vantare eccellenti strumenti per interfacciare diversi modelli fisici in un ambiente multifisica/multiscala. I modelli atomistici inclusi sono utili al calcolo delle deformazioni elastiche, della geometria della struttura e degli stati elettronici. Infine, viene presentata anche una tecnica inedita per una descrizione quantistica efficiente del trasporto di carica. Questo lavoro vuole contrubuire a rendere TiberCAD uno strumento di riferimento per la simulazione di dispositivi optoelettronici su nanoscala.The simulation of novel optoelectronic devices is a great challenge for the engineering community. The enoromous progress in device fabrication technology allowed such a massive downscaling that geometrical feature in the nanoscale play a crucial role. Furthermore we have a great effort in exploring alternative solutions respect to more traditional semiconductor devices. It involves molecular electronic, semiconductive polymers, self-assembled structures, quasi-one dimensional and two dimensional materials. In such scenario it's crucial to develop modular simulation tools able to connect different physical models on different length scales. Quantum effect play an important role and we need to take them into account, avoiding anyway an explosion of the computational complexity. Thus it's needed to go in the direction of a multiscale approach, which is already applied with success in mechanical science. The goal of this work is to include atomistic description and atomistic models in TiberCAD, a Technology CAD code for simulation of optoelectronic devices which can rely on excellent instruments for interfacing different models in a multyphisics/multiscale environment. Atomistic models for the calculation of strain, structure geometry and electronic states have been included. A novel technique for describing quantum transport with an efficient algorithm is also presented. These work wants to push TiberCAD to be a reference tool for calculation of complex optoeletronic devices at the nanoscale

A Self Energy Model of Dephasing in Molecular Junctions

Quantum decoherence plays an important role in the charge transport characteristics of molecular wires at room temperature. In this paper we propose a generalization of an electron–phonon dephasing model to non orthogonal LCAO basis. We implemented the model in combination with a density functional-based tight binding (DFTB) theory framework and utilized it to model charge transport characteristics of an anthraquinone (AQ) based molecular wire. We demonstrate a modulation of Quantum Interference (QI) effects compatible with experiments and confirm the robustness of QI signatures with respect to dephasing. An analysis of the spatial localization of the dephasing process reveals that both the QI and the dephasing process are localized in the AQ region, hence justifying the general robustness of the transmission temperature dependence in different AQ-based systems

Atomistic Modeling of Charge Transport across a Carbon Nanotube–Polyethylene Junction

The conduction mechanism in carbon nanotube (CNT) polymer nanocomposites is complex, and there has been a considerable amount of work invested in understanding the role of the distribution of the CNTs in the composite and how it influences the conductivity. However, less interest has been devoted to the electron transport across a single CNT–polymer–CNT junction. We present a first atomistic study of the electron transmission through a CNT–polyethylene–CNT junction. The morphology of the junction is described using classical molecular dynamics simulations, and transport properties are calculated within density functional tight binding method. The electron transmission depends noticeably on the CNT–CNT separation and on the consequent polymer wrapping. At CNT–CNT distances shorter than 6 Å, the polyethylene molecules do not penetrate in the space between the CNTs. In this near contact regime, the electron transmission proceeds via direct tunneling between the two CNTs across a vacuum region without relevant contribution from the surrounding polymer. For distances larger than 6 Å, the PE molecules enter into the junction region. The frontier orbitals of the PE molecules in the junction provide localized states, which can couple to the CNT metallic states. This resonance tail increases the electron transmission probability between the CNTs across the junction by several orders of magnitude, thus lowering the effective barrier. The gradual interpenetration of the polymer is resembled in transmission fluctuations. An averaging of the transmission in energy and time along MD trajectories allows a quantitative estimation of the junction resistance and tunneling barrier

Possibility of a Field Effect Transistor Based on Dirac Particles in Semiconducting Anatase-TiO₂ Nanowires

In Dirac materials, like graphene or topological insulators, massless pseudorelativistic electrons promise new, very fast electronic devices by utilizing the partial suppression of backscattering. However, the semimetal nature of graphene makes the realization of practical field effect transistors difficult, due to small on–off current ratios. Here, we propose a new concept, based on Dirac states <i>inside</i> the conduction (or valence) band of a lightly doped wide band gap semiconductor. With the application of a gate voltage, the Dirac states become populated; that is, the Fermi level is switched between the “classical” high-resistivity semiconducting and the relativistic high-mobility metallic range. We demonstrate by theoretical calculations that such a transition can be realized, for example, in thin anatase nanowires, which have been synthesized before. Ta-doped anatase nanowires offer an excellent possibility to build field effect transistors with high speed and good on–off ratio. Guidelines for finding similar “Dirac semiconductors” are provided