Summer 2023
- Carbon Capture with Nitrogen Assembly Carbons and Deep Eutectic Solvents: A New Generation of
Sorbents -
Carbon dioxide capture is considered as one of the crucial strategies to achieve the net-zero emission
goal by year 2050. In this proposal, various aspects of a new class of solid and liquid adsorbent
materials, nitrogen assembly carbons (NACs) and deep eutectic solvents (DESs), respectively, are
theoretically explored for carbon dioxide capture to enhance selectivity and capacity via physisorption
and chemisorption. In this work, three different moieties of NAC materials (graphitic, pyridinic, and
pyrrolic) are investigated as potential candidates to explore their surface properties and possible
reaction paths. Furthermore, solubility and possible CO2 chemisorption pathways of DES based on
ethylene glycol (EG) and ionic liquid (protonated monoethanolamine and imidazole) are investigated.
Based on molecular simulations accompanied by RI-MP2/6-31+G(d,p) quantum mechanical calculations
on NAC and DES should be able provide new prospective (performance-structure relationships, possible
reaction paths and associated barrier heights) on CO2 capture technology.
Mentor: Mark Gordon
Participants: Nuwan De Silva, Kyle Mascaro
Research Area: Physical Chemistry - Effect of atomic disorder on electronic and magnetic properties of Heusler alloys
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Materials exhibiting a high degree of spin polarization are in demand for applications in spintronics.
Room-temperature half-metals (HM) are considered ideal candidates, as they behave as an insulator for
one spin channel and as a conductor for the other spin channel. Ideally, HM materials could provide a
100% transport spin polarization for device applications in spin-based electronics, e.g. for spin-transfer
torque (STT) random-access memories (MRAM). Potential candidates exhibiting nearly 100% spin
polarization have been extensively studied in recent years, and many compounds have been proposed.
The main objective of the current proposal is to theoretically analyze the effect of atomic disorder on
electronic and magnetic properties of potentially half-metallic materials. The unique band structure of
HM materials typically requires well-defined atomic arrangements. The reason is that structural changes
modify the local densities of states (DOS) and amount to a smearing of the total DOS. As a result,
chemical substitutions and atomic disorder tend to reduce the spin polarization. At the same time,
atomic substitution may also create a half-metal. This was demonstrated in our recent work on Ti2MnAl,
a Heusler alloy, which undergoes a half-metallic transition, when 50% of Al atoms are replaces with Sn.
The purpose of the current proposal is to analyze similar mechanisms, when atomic disorder and
substitution modify the electronic and magnetic properties of half-metallic compounds. The results of
this work could serve as a guide for experimentalists working on various spintronic applications.
Mentor: Liqin Ke
Participants: Pavel Lukashev
Research Area: Condensed Matter Physics - Strong electron correlation in metal oxides and sulfides
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We study and analyze the strongly correlated pristine transition metal oxides such as Fe3O4, Cr3O4, and
those doped with other transition metals as well as the metal sulfides such as MnS2 and CrS2 to (i)
explore and understand the fundamental physics behind their electronic structure and magnetic
properties, (ii) applicability and tunability of these systems in the current technology and (iii) their
candidacy is the newly emerging field of quantum information system. The Fe3O4 has Fe in both
octahedral and tetrahedral sites providing two competing structures in its crystal, and the same
structural behavior is observed in Cr3O4 as well. Comparative studies of Fe3O4 with Cr3O4 and MnS2
with CrS2 are primarily interesting because they have contrasting fillings of 3d and 4s orbitals in
respective Fe, Cr, and Mn compositions. We explore how does the 3D bulk of these transition metal
oxides and their single-layer 2D counterparts behave in terms of magnetic ordering and magnetic phase
transition. Fe ions interacting magnetically with non-similar sites, namely the interacting
octahedral/tetrahedral pairs, yield antiferromagnetic ordering, whereas the octahedral-to-octahedral
ions interaction is ferromagnetic, resulting in the overall ferromagnetic ordering.
Mentor: Durga Paudyal
Participants: Chandra Mani Adhikari
Research Area: Condensed Matter Physics - Controlling polymer degradation using enzymatic nanofillers
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The development of plastics has enabled major improvements in packaging, storage, and transportation.
Nevertheless, these materials are fossil fuel-derived, hence, increases carbon footprint, and they
decompose at an extremely slow rate. Bioplastics promises a more sustainable future for the use of
plastics as they have been marketed as compostable materials. The conditions required, however, are
stringent and not suitable for most existing compost facilities. Thus, engineered degradation using
embedded enzymes will be key for bioplastics to be a truly sustainable material. The biggest hurdle is
cost associated with isolating the enzymes and the ability for on-demand degradation. We propose to
use seeds as a low-cost source for enzymes capable of breaking down bio-polyesters. Nanocomposites
will be fabricated using milled seeds embedded into the bio-derived plastic. We expect degradation of
the composite to be temperature activated by virtue of the optimum temperature of enzyme activity.
Furthermore, the size of the milled seeds should dictate degradation properties due to changes in
morphology of the semicrystalline plastics. This project will initiate the path to low cost engineered
degradation in bioplastics and will promote the use of bioplastics instead of their fossil fuel derived
counterparts
Mentor: Tanya Prozorov
Participants: Chamila Chandima De Silva
Research Area: Engineering Materials
Summer 2022
- Materials Design Based on First Principles for Permanent Magnets
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Currently, Nd2Fe14B and ferrites are the two main permanent magnets manufactured in the industry.
While Nd2Fe14B magnets are used mainly in high-end devices in which weight-to-power ratio is of
prime importance, ferrites find their place in products which do not require large magnetization. We
propose to develop materials design strategies based on first principles that guide selection and
optimization of permanent magnets with (BH)max values, the energy product for a given volume of the
magnetic material, between the best ferrite magnets and Nd–Fe–B type magnets in an attempt to fill
the empty niche of energy products. Our approach has multiple facets including: (i) Performing detailed
electronic structure calculations that reveal the effective magnetic moment, exchange coupling, and
magnetic anisotropy in Pauli paramagnets with ternary or quaternary additions to assess the prospect of
using them as inexpensive permanent magnets. (ii) Determining the role of ternary and quaternary
additions in tuning the magnetic moment and exchange interactions in anisotropic structures by careful
control of atomic site distribution to maximize both properties. (iii) Identifying the effective sites for
non-critical element substitutions to enhance the magnetic anisotropies in uniaxial crystal structures.
Successful completion of these goals will help us elucidate the role of ternary and quaternary additions
in changing the density of states of each class of materials listed above. The knowledge gained from this
research will potentially help with benchmarking new ferromagnetic alloys that could serve as “gap
magnets”.
Mentor: Durga Paudyal
Participants: Huseyin Ucar
Research Area: Materials Science - Computational Modeling of Defects for Quantum Information Science Application
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The rare-earth-based iron garnets (RIGs) have attracted significant attraction because of their wide
technological applications such as microwaves, optics, acoustics, magneto-optics, lasers, data storage,
spintronics, and potentially in quantum information devices. In order to realize their potential
applications, atomic-level details of the electronic, magnetic, intrinsic defect, and doping behavior in
those materials need to be understood. Using first-principles calculations, we investigate the above
properties in yttrium iron garnet (YIG). In addition, the role of rare-earth doping in YIG and its impact on
magnetic exchange interaction and defect states will be explored. Moreover, incorporation of the rare-
earth ions in YIG can potentially provide the defects with long spin coherence and stable optical
transition. Moreover, electronic, magnetic, and topological properties of novel materials such as R2T,
where R = Eu, Gd or Yb, and T= In, Sn, and Sb. will also be studied.
Mentor: Durga Paudyal
Participants: Santosh KC
Research Area: Materials Science
Summer 2020
- Development of Accurate Effective Force Field From ab initio Molecular Dynamics Simulation Using Coarse-graining Approach
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Computer simulation methods have become more popular in predicting properties of complex systems with recent advances in high-performance computing. When provided with an accurate force field a computer simulation approach will accurately predict properties of a system of interest. Quantum-mechanical (QM) methods deliver the most reliable and accurate properties prediction by taking into account the electronic behavior from first principles. However, QM approaches are computationally expensive and typically used with smaller systems. Classical or molecular mechanics methods are much faster but less accurate due to use of empirical force fields. The focus of this project is to coarse-grain the electronic structure out of a system, but maintain all of the atoms, thus converting a quantum atomistic molecule into a classical atomistic molecule by coarse-graining. In conventional coarse-graining approaches the effect of the electron structure is averaged out and represented in the form of pair interaction mean forces so that relevant timescale information is lost. This leads to inaccurate predictions of the dynamics and transport properties. A novelty of the proposed project is in the application of recently developed coarse-graining approach to recover timescales lost during a coarse-graining procedure. As a result of this project, an accurate force field for the classical atomistic system will be developed based on first principles ab initio method. This will allow one to perform large-scale atomistic simulations with QM-accuracy. The target system of this project is the suite of heterogeneous catalysts called mesoporous silica nanoparticles that are synthesized and studied theoretically in the Ames Laboratory.
Mentor: Mark Gordon, distinguished professor of Chemistry, Iowa State University
- N-Doped Nanoporous Carbon Monolith Synthesis and the Application for Electrocatalysis
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Doping nitrogen within porous carbon skeleton has been demonstrated that it is a powerful approach to tuning electronic properties and/or conductivity, which thus facilitate their applications, particularly in electrocatalysis. Meanwhile, the electrocatalysis performance of N-doped carbon materials strongly depends on the density of the active sites and how these active sites are distributed in the skeleton. Thus, the development of new synthetic methods is the key for creation of advanced N-doped carbon materials for electrocatalysis. In order to prepare N-doped carbon catalysts, herein we propose to develop a novel synthetic methodology which includes a template-free synthesis of polymeric monolith precursors and afterward high temperature carbonation step.
There are four innovations involved in this project. First, a facile method will be used to prepare polymer precursors based on one step radical polymerization without any template agents. The porous monolithic polymer precursor can be converted to carbon monoliths with uniform nitrogen decoration and high porosity of precursors can be partially preserved to afford high surface area of resultant carbons via facile pyrolysis. The second innovation is the high surface area and nanosized pores guarantee the free diffusion of oxygen and electrolyte to the catalytic active sites through short diffusion path lengths. The third innovation involves improvements in electrocatalysis with a homogeneous distribution of nitrogen atoms. Finally, the monolithic N-doped carbon, compared to carbon powder, can be easily recovered and reused for many times. This should form the foundation for a new generation of high surface area carbon catalysts for electrocatalysis.
Mentor: Wenyu Huang, assistant professor of chemistry, Iowa State University