Influence of long-range interactions on charge ordering phenomena on a square lattice

Usually complex charge ordering phenomena arise due to competing interactions. We have studied how such ordered patterns emerge from the frustration of a long-ranged interaction on a lattice. Using the lattice gas model on a square lattice with fixed particle density, we have identified several interesting phases; such as a generalization of Wigner crystals at low particle densities and stripe phases at densities in between rho = 1/3 and rho = 1/2. These stripes act as domain walls in the checkerboard phase present at half-filling. The phases are characterised at zero temperatures using numerical simulations, and mean field theory is used to construct a finite temperature phase diagram.Comment: 8 pages, 8 figure

Modeling the layer-by-layer growth of HKUST-1 metal-organic framework thin films

Metal organic frameworks have emerged as an important new class of materials with many applications, such as sensing, gas separation, drug delivery. In many cases, their performance is limited by structural defects, including vacancies and domain boundaries. In the case of MOF thin films, surface roughness can also have a pronounced influence on MOF-based device properties. Presently, there is little systematic knowledge about optimal growth conditions with regard to optimal morphologies for specific applications. In this work, we simulate the layer-by-layer (LbL) growth of the HKUST-1 MOF as a function of temperature and reactant concentration using a coarse-grained model that permits detailed insights into the growth mechanism. This model helps to understand the morphological features of HKUST-1 grown under different conditions and can be used to predict and optimize the temperature for the purpose of controlling the crystal quality and yield. It was found that reactant concentration affects the mass deposition rate, while its effect on the crystallinity of the generated HKUST-1 film is less pronounced. In addition, the effect of temperature on the surface roughness of the film can be divided into three regimes. Temperatures in the range from 10 to 129 °C allow better control of surface roughness and film thickness, while film growth in the range of 129 to 182 °C is characterized by a lower mass deposition rate per cycle and rougher surfaces. Finally, for T larger than 182 °C, the film grows slower, but in a smooth fashion. Furthermore, the potential effect of temperature on the crystallinity of LbL-grown HKUST-1 was quantified. To obtain high crystallinity, the operating temperature should preferably not exceed 57 °C, with an optimum around 28 °C, which agrees with experimental observations

RE-DESAIN SISTEM PENDINGINAN BIJI KOPI PADA BLOWER COOLANT TRAY MESIN ROASTING KOPI PRATTER PT. PATMANUNGGAL REKA ABADI

AbstrakKualitas kopi ditentukan oleh penangananselama panen dan pasca panen. Biji kopi dihasilkan melalui proses pengupasan, pencucian, pengeringan, dan roasting. Pada proses roasting, pemilihan bloweruntuk pendingin merupakan aspek penting. Masalah yang terjadi pada sistem pendinginan mesin roasting kopi pratter kapasitas 1,5 kg adalah pemilihan blower kurang optimal dikarenakan waktu pendinginan lama. Penelititan tentang blower pada sistem coolant tray bertujuan mengatasi permasalahan tersebut, sehingga cita rasa kopi tidak berubah setelah proses roasting. Mesin roasting memiliki bagian utama yang berfungsi untuk menurunkan suhu panas pada kopi yaitu blower coolant tray. Fokus penelitian terletak pada pembuatan blower yang sesuai dengan perhitungan rumus heat transfer dengan parameter berupa penurunan suhu dari 170° C menjadi 35° C dengan mempertimbangkan hasil kecepatan pendinginan pada blower serta faktor yang dapat meningkatkan daya hisap volume udara. Hasil perhitungan menghasilkan blower dengan dimensi 301 x 358 x 246 mm, panjang ducting pipa 400 mm, dan penggerak motor 2 HP dengan putaran 3000 rpm. Hasil simulasi software solidwork menggunakan fitur CFD (Computational Fluid Dynamics) didapatkan tingkat kecepatan hisap sebesar 2,359 m/s dan daya hisap volume sebesar 0,000115m3/s.Kata Kunci: Blower, heat transfer, CFD, roasting.AbstractCoffee quality is determined by handling during harvest and post-harvest.Coffee beans are produced through the process of peeling, washing, drying and roasting.In the roasting process, the selection of blowers for cooling is an important aspect.The problem that occurs in the cooling system for a pratter coffee roasting machine with a capacity of 1.5 kg is that the selection of the blower is not optimal due to the long cooling time.Research on blowers on coolant tray systems aims to overcome these problems, so that the taste of coffee does not change after the roasting process.The roasting machine has the main part that functions to reduce the heat temperature of the coffee, namely the blower coolant tray.The focus of the research lies in making a blower according to the calculation of the heat transfer formula with parameters in the form of a temperature drop from 170° C to 35° C by considering the results of the cooling speed of the blower and factors that can increase the suction power of the air volume.The calculation results produce a blower with dimensions of 301 x 358 x 246 mm, a ducting pipe length of 400 mm, and a 2 HP motor drive with 3000 rpm rotation.Solidwork software simulation results using the CFD (Computational Fluid Dynamics) feature obtained a suction speed level of 2.359 m/s and a volume suction power of 0.000115 m3/s.Keywords: Blowers, heat transfer, CFD, roasting

Crystalline assembly of perylene in metal–organic framework thin film: J-aggregate or excimer? Insight into the electronic structure

The spatial orientation of chromophores defines the photophysical and optoelectronic properties of a material and serves as the main tunable parameter for tailoring functionality. Controlled assembly for achieving a predefined spatial orientation of chromophores is rather challenging. Metal–organic frameworks (MOFs) are an attractive platform for exploring the virtually unlimited chemical space of organic components and their self-assembly for device optimization. Here, we demonstrate the impact of interchromophore interactions on the photophysical properties of a surface-anchored MOF (SURMOF) based on 3,9-perylenedicarboxylicacid linkers. We predict the structural assembly of the perylene molecules in the MOF via robust periodic density functional theory calculations and discuss the impact of unit topology and π-π interaction patterns on spectroscopic and semiconducting properties of the MOF films. We explain the dual nature of excited states in the perylene MOF, where strong temperature-modulated excimer emission, enhanced by the formation of perylene J-aggregates, and low stable monomer emission are observed. We use band-like and hopping transport mechanisms to predict semiconducting properties of perylene SURMOF-2 films as a function of inter-linker interactions, demonstrating both p-type and n-type conduction mechanisms. Hole carrier mobility up to 7.34 cm2/Vs is predicted for the perylene SURMOF-2. The results show a promising pathway towards controlling excimer photophysics in a MOF while controlling charge carrier mobility on the basis of a predictive model

Resolving the Role of Configurational Entropy in Improving Cycling Performance of Multicomponent Hexacyanoferrate Cathodes for Sodium‐Ion Batteries

Mn-based hexacyanoferrate (Mn-HCF) cathodes for Na-ion batteries usually suffer from poor reversibility and capacity decay resulting from unfavorable phase transitions and structural degradation during cycling. To address this issue, the high-entropy concept is here applied to Mn-HCF materials, significantly improving the sodium storage capabilities of this system via a solid-solution mechanism with minor crystallographic changes upon de-/sodiation. Complementary structural, electrochemical, and computational characterization methods are used to compare the behavior of high-, medium-, and low-entropy multicomponent Mn-HCFs resolving, to our knowledge for the first time, the link between configurational entropy/compositional disorder (entropy-mediated suppression of phase transitions, etc.) and cycling performance/stability in this promising class of next-generation cathode materials

Tuning Optical Properties by Controlled Aggregation: Electroluminescence Assisted by Thermally‐Activated Delayed Fluorescence from Thin Films of Crystalline Chromophores

Several photophysical properties of chromophores depend crucially on intermolecular interactions. Thermally‐activated delayed fluorescence (TADF) is often influenced by close packing of the chromophore assembly. In this context, the metal‐organic framework (MOF) approach has several advantages: it can be used to steer aggregation such that the orientation within aggregated structures can be predicted using rational approaches. We demonstrate this design concept for a DPA‐TPE (diphenylamine‐tetraphenylethylene) chromophore, which is non‐emissive in its solvated state due to vibrational quenching. Turning this DPA‐TPE into a ditopic linker allows to grow oriented MOF thin films exhibiting pronounced green electroluminescence with low onset voltages. Measurements at different temperatures clearly demonstrate the presence of TADF. Finally, we show that the layer‐by‐layer process used for MOF thin film deposition allowed to integrate the TADF‐DPA‐TPE in a functioning LED device

Anionen‐Einlagerungschemie organischer Kathoden für zweiwertige Metallbatterien mit hoher Energie und hoher Leistungsdichte

Multivalente Batterien sind sehr vielversprechend für nachhaltige Energiespeicheranwendungen der nächsten Generation. Hier berichten wir über eine Polytriphenylamin (PTPAn)‐Verbundkathode, die in der Lage ist, Tetrakis(hexafluorisopropyloxy)borat [B(hfip)₄]⁻ Anionen in sowohl Magnesium‐ (Mg) als auch Calcium‐ (Ca) Batteriesystemen hochreversibel zu speichern. Spektroskopische und Computerstudien zeigen den Redoxreaktionsmechanismus des PTPAn‐Kathodenmaterials. Die Mg‐ und Ca‐Zellen weisen eine Zellspannung von ∼3 V, eine hohe Leistungsdichte von ∼3000 W kg⁻¹ bzw. eine hohe Energiedichte von ∼300 Wh kg⁻¹ auf. Darüber hinaus könnte die Kombination der PTPAn‐Kathode mit einer Anode aus einer Calcium‐Zinn‐Legierung (Ca−Sn) eine lange Batterielebensdauer von 3000 Zyklen bei einer Kapazitätserhaltung von 60 % ermöglichen. Die Anionenspeicherchemie in Verbindung mit dem elektrochemischen Doppelionenkonzept demonstriert einen neuen gangbaren Weg zu Hochleistungsbatterien mit zweiwertigen Ionen