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Dive into the research topics where Roman Nazarov is active.

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Featured researches published by Roman Nazarov.


New Journal of Physics | 2015

Rapid theory-guided prototyping of ductile Mg alloys: from binary to multi-component materials

Zongrui Pei; Martin Friák; Stefanie Sandlöbes; Roman Nazarov; Bob Svendsen; Dierk Raabe; Jörg Neugebauer

In order to identify a method allowing for a fast solute assessment without lengthy ab initio calculations, we analyze correlations and anti-correlation between the stacking fault energies (SFEs), which were shown to be related to the macroscopic ductility in Mg alloys, and five material parameters of 18 different elemental solutes. Our analysis reveals that the atomic volume V of pure solutes, their electronegativity ν and bulk modulus B are either linearly or logarithmically related to the SFE. Comparing the impact of solutes with that of yttrium (that increases the ductility in Mg) we propose a single numerical quantity (called yttrium similarity index, YSI) that is based on these inter-relations. Subsequently, we evaluate this new figure of merit for 76 elements from the periodic table of elements in search for solutes reducing the SFE. Limiting ourselves first to binary Mg alloys, we hardly find any alternative solutes providing similar reduction as that due to rare-earth (RE) additions. Therefore, we extended our search to ternary Mg alloys. Assuming that the physical properties of solute combinations can be represented by their average values, 2850 solute combinations were checked and 133 solute pairs (not including any RE elements) have been found to have a YSI larger than 0.85. Quantum-mechanical calculations have been subsequently performed for 11 solute pairs with YSIs higher than 0.95 and they were all found to reduce the in excellent agreement with the predictions based on the YSI.


Physical Review B | 2017

Ab initio explanation of disorder and off-stoichiometry in Fe–Mn–Al–C κ carbides

Poulumi Dey; Roman Nazarov; Biswanath Dutta; Mengji Yao; Michael Herbig; Martin Friák; Tilmann Hickel; Dierk Raabe; Jörg Neugebauer

Carbides play a central role for the strength and ductility in many materials. Simulating the impact of these precipitates on the mechanical performance requires knowledge about their atomic configuration. In particular, the C content is often observed to substantially deviate from the ideal stoichiometric composition. In this work, we focus on Fe-Mn-Al-C steels, for which we determined the composition of the nanosized


Energy and Environmental Science | 2018

An assessment of strategies for the development of solid-state adsorbents for vehicular hydrogen storage

Mark D. Allendorf; Zeric Hulvey; Thomas Gennett; Alauddin Ahmed; Tom Autrey; Jeffrey Camp; Eun Seon Cho; Hiroyasu Furukawa; Maciej Haranczyk; Martin Head-Gordon; Sohee Jeong; Abhi Karkamkar; Di-Jia Liu; Jeffrey R. Long; Katie R. Meihaus; Iffat H. Nayyar; Roman Nazarov; Donald J. Siegel; Vitalie Stavila; Jeffrey J. Urban; Srimukh Prasad Veccham; Brandon C. Wood

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Physical Review B | 2010

First-principles study of the thermodynamics of hydrogen-vacancy interaction in fcc iron

Roman Nazarov; Tilmann Hickel; J. Neugebauer

carbides (Fe,Mn)


Physical Review B | 2012

Vacancy formation energies in fcc metals: Influence of exchange-correlation functionals and correction schemes

Roman Nazarov; Tilmann Hickel; Jörg Neugebauer

{}_{3}\mathrm{AlC}


Physical Review B | 2014

Ab initio study of H-vacancy interactions in fcc metals: Implications for the formation of superabundant vacancies

Roman Nazarov; Tilmann Hickel; Jörg Neugebauer

by atom probe tomography in comparison to larger precipitates located in grain boundaries. Combining density functional theory with thermodynamic concepts, we first determine the critical temperatures for the presence of chemical and magnetic disorder in these carbides. Second, the experimentally observed reduction of the C content is explained as a compromise between the gain in chemical energy during partitioning and the elastic strains emerging in coherent microstructures.


Physical Review B | 2016

First-principles investigation of hydrogen interaction with TiC precipitates in α -Fe

Davide Di Stefano; Roman Nazarov; Tilmann Hickel; Jörg Neugebauer; Matous Mrovec; Christian Elsässer

Nanoporous adsorbents are a diverse category of solid-state materials that hold considerable promise for vehicular hydrogen storage. Although impressive storage capacities have been demonstrated for several materials, particularly at cryogenic temperatures, materials meeting all of the targets established by the U.S. Department of Energy have yet to be identified. In this Perspective, we provide an overview of the major known and proposed strategies for hydrogen adsorbents, with the aim of guiding ongoing research as well as future new storage concepts. The discussion of each strategy includes current relevant literature, strengths and weaknesses, and outstanding challenges that preclude implementation. We consider in particular metal–organic frameworks (MOFs), including surface area/volume tailoring, open metal sites, and the binding of multiple H2 molecules to a single metal site. Two related classes of porous framework materials, covalent organic frameworks (COFs) and porous aromatic frameworks (PAFs), are also discussed, as are graphene and graphene oxide and doped porous carbons. We additionally introduce criteria for evaluating the merits of a particular materials design strategy. Computation has become an important tool in the discovery of new storage materials, and a brief introduction to the benefits and limitations of computational predictions of H2 physisorption is therefore presented. Finally, considerations for the synthesis and characterization of hydrogen storage adsorbents are discussed.


JOM | 2014

Ab initio based understanding of the segregation and diffusion mechanisms of hydrogen in steels

Tilmann Hickel; Roman Nazarov; Eunan McEniry; Gerard Leyson; Blazej Grabowski; Jörg Neugebauer


Physical Review B | 2016

Benchmarking the pseudopotential and fixed-node approximations in diffusion Monte Carlo calculations of molecules and solids

Roman Nazarov; Luke Shulenburger; Miguel Morales; Randolph Q. Hood


Physical Review B | 2016

First-principles calculation of the elastic dipole tensor of a point defect: Application to hydrogen in α-zirconium

A. P. Sutton; Roman Nazarov; Js Majevadia; M Patel; Wenman; Ds Balint; J. Neugebauer

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Martin Friák

Academy of Sciences of the Czech Republic

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Randolph Q. Hood

Lawrence Livermore National Laboratory

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