New inversion boundary structure in Sb-doped ZnO predicted by DFT calculations and confirmed by experimental HRTEM

Today, ab-initio calculations are becoming a powerful tool to perform virtual experiments that have the capacity to predict and to reproduce experimentally observed non-periodic features, such as interfaces, that are responsible for quantum properties of materials. In our paper we investigate 2D quantum-well structures, known as inversion boundaries OM. Combining atomistic modeling, DFT calculations and HRTEM analysis we provide a new fundamental insight into the structure and stability of Sb-rich basal-plane IBs in ZnO. DFT screening for potential IB model was based on the known stacking deviations in originating wurtzite structure. The results show that the model with A beta-B alpha-A beta C-gamma B-beta C sequence (IB3) is the most stable translation for Sb-doping, as opposed to previously accepted A beta-B alpha-A beta C-gamma A-alpha C (IB2) model. The key to the stability of IB structures has been found to lie in their cationic stacking. We show that the energies of constituting stacking segments can be used to predict the stability of new IB structures without the need of further ab-initio calculations. DFT optimized models of IBs accurately predict the experimentally observed IB structures with lateral relaxations down to a precision of similar to 1 pm. The newly determined cation sublattice expansions for experimentally confirmed IB2 and IB3 models, Delta(IB(zn-zn)) are +81 pm and +77 pm, whereas the corresponding O-sublattice contractions Delta(IB(0-0)) are -53 pm and -57 pm, respectively. The refined structures will help to solve open questions related to their role in electron transport, phonon scattering, p-type conductivity, affinity of dopants to generate IBs and the underlying formation mechanisms, whereas the excellent match between the calculations and experiment demonstrated in our study opens new perspectives for prediction of such properties from first principles

Corrosion resistance of crystalline and amorphous CuZr alloys in NaCl aqueous environment and effect of corrosion inhibitors

CuZr alloys are the basis of a family of metallic glasses with large glass forming ability and remarkable mechanical properties. The corrosion response of prepared crystalline and amorphous CuxZr100-x alloys (x = 40, 50, 64 at%), as well as bare Cu and Zr, in a severe corrosive environment, was tested. The alloys were immersed in 3 wt% NaCl aqueous solution. With the aim to increase the resistance of copper as less corrosion alloy component, nine imidazole-based compounds with different functional groups were tested as potential corrosion inhibitors. Potentiodynamic polarization measurements, electrochemical impedance spectroscopy, and long-term immersion tests followed by X-ray photoelectron spectroscopy and microscopy analysis were carried out. Overall, all the tested amorphous alloys exhibit a much better corrosion resistance than their crystalline counterparts in the presence and absence of inhibitors. The main factor controlling the corrosion resistance of the alloys appears to be the Zr-rich (or at least equiatomic) amorphous structure, the effect of the inhibitors being secondary. Results therefore show a complex relationship between inhibitor performance, microstructure and composition of CuZr alloys.Peer ReviewedPostprint (published version

Improving the HER Activity and Stability of Pt Nanoparticles by Titanium Oxynitride Support

Water electrolysis powered by renewables is regarded as the feasible route for the production of hydrogen, obtained at the cathode side through electrochemical hydrogen evolution reaction (HER). Herein, we present a rational strategy to improve the overall HER catalytic performance of Pt, which is known as the best monometallic catalyst for this reaction, by supporting it on a conductive titanium oxynitride (TiONx) dispersed over reduced graphene oxide nanoribbons. Characterization of the Pt/TiONx composite revealed the presence of small Pt particles with diameters between 2 and 3 nm, which are well dispersed over the TiONx support. The Pt/TiONx nanocomposite exhibited improved HER activity and stability with respect to the Pt/C benchmark in an acid electrolyte, which was ascribed to the strong metal–support interaction (SMSI) triggered between the TiONx support and grafted Pt nanoparticles. SMSI between TiONx and Pt was evidenced by X-ray photoelectron spectroscopy (XPS) through a shift of the binding energies of the characteristic Pt 4f photoelectron lines with respect to Pt/C. Density functional theory (DFT) calculations confirmed the strong interaction between Pt nanoparticles and the TiONx support. This strong interaction improves the stability of Pt nanoparticles and weakens the binding of chemisorbed H atoms thereon. Both of these effects may result in enhanced HER activity

Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials

Quantum ESPRESSO is an integrated suite of computer codes for electronic-structure calculations and materials modeling, based on density-functional theory, plane waves, and pseudopotentials (norm-conserving, ultrasoft, and projector-augmented wave). Quantum ESPRESSO stands for "opEn Source Package for Research in Electronic Structure, Simulation, and Optimization". It is freely available to researchers around the world under the terms of the GNU General Public License. Quantum ESPRESSO builds upon newly-restructured electronic-structure codes that have been developed and tested by some of the original authors of novel electronic-structure algorithms and applied in the last twenty years by some of the leading materials modeling groups worldwide. Innovation and efficiency are still its main focus, with special attention paid to massively-parallel architectures, and a great effort being devoted to user friendliness. Quantum ESPRESSO is evolving towards a distribution of independent and inter-operable codes in the spirit of an open-source project, where researchers active in the field of electronic-structure calculations are encouraged to participate in the project by contributing their own codes or by implementing their own ideas into existing codes.Comment: 36 pages, 5 figures, resubmitted to J.Phys.: Condens. Matte

Angular distributions of desorbing N2 in thermal N2O decomposition on Rh(100)

The angular distribution of desorbing N2 was studied in the decomposition of N2O(a) on Rh(1 0 0) at 60–140 K by means of angle-resolved temperature-programmed desorption. N2 desorption shows two peaks at around 80 K and 110 K. At low N2O coverage, the former collimates far from the surface normal toward the [0 0 1] direction, whereas at high coverage, the desorption sharply collimates along the surface normal. The adsorption form of N2O and its dissociation were also examined by DFT-GGA calculations. Dissociating N2O is proposed to be lying along the [0 0 1] direction at low coverage and to change to an upright form bonding through the terminal oxygen at high coverage

Optimization of processes in service activity of household appliances

V podjetju Gorenje so pred približno desetimi leti projektirali sodoben servis s hitro odzivnostjo. Za stranko je to pomenilo eno najboljših servisnih strežb na področju gospodinjskih aparatov. Podjetje si je pridobilo pomembno prednost pred konkurenco in prodaja je sčasoma začela naraščati. Za serviserje gospodinjskih aparatov je sistem izredno motivacijsko naravnan s poudarkom na nagrajevanju po učinku. Zmanjševanje stroškov in števila zaposlenih serviserjev ter prilagajanje strankam je v nekaj letih povzročilo preobremenitev serviserjev. Poleg tega se serviserji vedno bolj zavedajo medsebojnih razlik glede nagrajevanja. Največji problem pri tem predstavlja logistika. Rešitev smo oblikovali na podlagi analiz servisnega procesa in statističnih podatkov. Za osrednji problem smo pri tem izpostavili preobremenitev serviserja. Prenova je grajena na procesih priprave serviserja, načrtovanja in izvedbe logistike, servisiranja in odpremljanja zamenjanih rezervnih delov aparatov v garanciji nazaj v podjetje. S predlagano rešitvijo smo izboljšali delovne razmere, logistiko serviserja in učinkovitost poslovanja, obdržali sloves hitrega in dobrega servisa ter zmanjšali stroške.At the company Gorenje a modern service with quick responsiveness was planned about ten years ago. For the customer on one hand, this meant one of the best service centre in the field of household appliances and for the company on the other hand, this renovation has obtained significant priority among other competitor companies. As the result, the sale eventually began to rise. The system has an extremely motivational attitude, focusing up on the after-effect remuneration, which is a big advantage for their people, but cutting costs and the number of employees in a few years led to staff’s overload. Furthermore, people are more and more aware of difference between them regarding the reward and the main issue of this present their logistics. The solution was developed based on the analysis of the service centre and statistical data. In the process, the central problem was the repairmen’s overload. Reform of the system is built on preparation process of the maintenance men, planning and performance of logistics, maintenance check and dispatching of exchanged spare parts of appliances under Gorenje’s warranty. With the proposed solution, we improved working conditions, repairmen’s logistics and business efficiency. We kept reputation of the “fast and good service” and reduced our costs

Digital transformation and optimization of servicing processes in the area of household appliances

Obravnava magistrske naloge zajema problematiko vse manj učinkovitih poslovnih procesov servisiranja gospodinjskih aparatov in neenakovreden nagradno–motivacijski sistem za serviserje podjetja Gorenje. Skozi teorijo spoznavamo literaturo različnih avtorjev s področja strukturne, operativne učinkovitosti procesov, logistike in motivacije, ki jo uporabimo v analiziranju servisnih procesov: ̶ analiza aktivnosti podprocesa klicni center pokaže predolg čakalni čas na prostega klicnega operaterja, ̶ analiza podprocesa vnosa reklamacij v aplikacijo razkrije vrsto podvojenega dela in veliko možnost napačnega vnosa, ̶ analiza podprocesa razdeljevanja reklamacij med serviserje pokaže problem v logistiki, ̶ analiza podprocesa obdelave reklamacij predoči veliko administrativno obremenitev za serviserja, ̶ analiza podprocesa kreiranja potnega naloga pokaže pretežno nevešče načrtovanje serviserja, ̶ analiza podprocesa servisiranja pa kaže na različno obremenitev serviserjev in ̶ analiza motivacijsko–nagradnega sistema pokaže, da plačevanje po učinku ni enako pravično za vse serviserje, saj je iz nagrade izvzeta vožnja med strankami. V empiričnem delu s pomočjo sodobnih optimizacijskih orodij kreiramo strukturno in operacijsko učinkovite servisne procese. V podprocesu klicni center ni več čakajočih strank na strežbo in operaterji so razbremenjeni, v podprocesu vnosa reklamacij se pretežni del s predhodno registracijo odvija aplikativno, prav tako v podprocesih razdelitev reklamacij in obdelave reklamacij, kot je na primer naročilo materialakreacija potnega naloga poteka avtomatsko. Za razbremenitev in motivacijo so bili z raziskavo razviti trije nagradno–motivacijski sistemi, od katerih je najpravičnejši plačevanje po efektu oziroma plačevanje po efektivnem času dela in po času vožnje do strank. V sklopu sodelovanja s Špelo Dolenc, ki je v svojem magistrskem delu z anketiranjem serviserjev Gorenja proučevala vpliv digitalne preobrazbe in optimizacije procesov na motivacijo in zadovoljstvo serviserjev gospodinjskih aparatov, se je skozi kreacijo obeh magistrskih nalog razvijala občasna diskusija, ki širše osvetljuje problematiko in nakazuje še vrsto drugih rešitev.This master\u27s thesis covers the problem of increasingly less efficient business processes of servicing household appliances and an unequal reward-motivation system for the repairmen of Gorenje. Through theory, we get to know the literature of various authors in the field of structural and operational efficiency of processes, logistics and motivation, which we use in analyzing service processes: • The analysis of the activity of the call center sub-process shows an excessively long waiting time for a free call operator • the analysis of the sub-process of entering complaints into the application reveals a type of duplicated work and a high possibility of incorrect entry • the analysis of the sub-process of distributing complaints between service technicians shows a problem in logistics, • the analysis of the sub-process of processing complaints shows a large administrative burden for service technician, • the analysis of the travel order creation sub-process shows mostly unskilled planning by the service technician, • the analysis of the servicing sub-process shows a different load on the service technicians, and • the analysis of the incentive-reward system shows that performance-based payment is not equally fair for all service technicians, as driving between customers is excluded from the reward. In empirical work, we create structurally and operationally efficient service processes with the help of modern optimization tools. As a result, in the call center sub-process, there are no more customers waiting for service and the operators are relieved, in the sub-process of entering complaints, the majority of the work takes place in an applicative manner with preliminary registration. In the sub-processes of distributing complaints and processing complaints, such as ordering materials and creating a travel order, the process takes place automatically. Three reward-motivation systems were developed through the research in order to increase the employee’s work motivation and create better workplace environment. As shown in the results of empirical part, the most appropriate is reward payment per worker’s effect, or variable payment defined by distinguishing between effective working time and by driving time to customers. As part of the cooperation with Špela Dolenc, who in her master\u27s thesis by surveying Gorenje repairmen, studied the impact of digital transformation and optimization of processes on the motivation and satisfaction of household appliance repairmen, an occasional discussion developed through the creation of both master\u27s theses, which sheds more light on the issue and indicates a type of other solutions

Corrosion Inhibition

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