Research group

Project: Computational screening of cathode materials for Zn-ion aqueous rechargeable batteries

Alongside the transformations on energy production and consumption, its storage must become more efficient, clean and cost-effective for the complete environmental impact to be as minimum as possible. Zn-ion aqueous batteries present itself as a promising candidate for future deployment, as it is described as a safer option than the technology used today. Therefore, the objective of this project is to utilize DFT calculations in the proposition of novel cathode materials for Zn-ion battery, and ultimately bridging the gap for achieving real-world products.

Publications/presentations:

• "Roadmap for the development of transition metal oxide cathodes for rechargeable zinc-ion batteries" J. Phys. Chem. C 128, 17261-17273 (2024)
• 245th Electrochemical Society Meeting (San Francisco, USA, May 2024)
• "Computational screening of cathode materials for Zn-ion rechargeable batteries" arXiv:2212.05396 [cond-mat.mtrl-sci] (2022)

Awards:

• McMaster university engineering graduate society travel award (2024)

Co-supervisor: Dr. Drew Higgins

Caio Miliante (PhD student, 2022-)

Project: Calculation of a topological invariant (Chern number) with WIEN2k

Topological materials are new phases of matter that led to a paradigm shift in their theoretical description, being necessary to use new concepts such as a Berry phase. These new matter phases are characterized by a global property of their electronic structure, i.e., a topological invariant (Chern number). The objective of our project is to implement a program for calculating this quantity as an extension of the all-electron DFT package WIEN2k.

Publications/presentations:

• "Understanding the chemical and structural variability in the efficiency of band edge optical transitions of 2D monolayer materials" arXiv [doi:10.48550/arXiv.2409.18287] (2024)
• 27th WIEN2k Hands-On Workshop for New and Existing Users (Trieste, Italy, April 2024)
• "Software implementation for calculating Chern and Z₂ topological invariants of crystalline solids with WIEN2k all-electron density functional package" Computer Phys. Commun. 292, 108864 (2023)

Awards:

• Mitacs Globalink Research Internship (2022)

Andres F. Gómez-Bastidas (Master student, 2023-; Undergraduate summer student, 2022)

Project: Surface functionalization of iron oxide nanoparticle for printable energy storage

Supercapacitors are gaining traction as alternative energy storing devices in many applications such as electronic devices and electric and hybrid vehicles. This project is responsible for electrode material and fabrication methods for supercapacitors to progress performance and cost developments. Goals for this project include successful fabrication of supercapacitor electrodes to be tested for performance. Investigation of dispersants for electrophoretic deposition will be done experimentally and theoretically to determine which molecules are best for iron oxide nanoparticle and carbon nanotube dispersion, and to understand underlying adhesion and bonding mechanisms.

Publications:

• "Application of murexide as a capping agent for fabrication of magnetite anodes for supercapacitors: experimental and first-principle studies" J. Mater. Sci. 59, 5480-5497 (2024)
• "Supercapacitor performance of magnetite nanoparticles enhanced by a catecholate dispersant: experiment and theory" Molecules 28, 1562 (2023)

Co-supervisor: Dr. Igor Zhitomirsky

Coulton Boucher (Master student, 2021-)

Project: Computational selection of aqueous zinc-ion battery cathode material

Rechargeable multivalent metal-ion batteries are being investigated as a safer and more reliable option. Among the potential options, zinc stands out as a promising candidate due to its cost-effectiveness, non-toxic nature, high theoretical capacity, and stability in aqueous electrolytes. Nevertheless, the incorporation of mobile cations into proposed cathodes poses challenges because of the strong electrostatic interaction. The primary objective of the project is to identify materials that exhibit improved ion intercalation/deintercalation capabilities with enhanced electrochemical stability, while also maintaining a workable pH to ensure long-term battery performance. This will be achieved through a thorough analysis of void structure and Pourbaix diagrams.

Yingzhu Zhou (Undergraduate Research Assistant, 2023)

Project: Screening optical properties of 2D materials

Two-dimensional (2D) materials, which consist of single or few atom layers, have emerged as a fascinating class of materials with exceptional optical properties. This project aims to take a computational approach using the VASP package to perform first principle calculations, helping us understand and classify these 2D materials based on their optical properties.

Publications/presentations:

• "Understanding the chemical and structural variability in the efficiency of band edge optical transitions of 2D monolayer materials" arXiv [doi:10.48550/arXiv.2409.18287] (2024)

Awards:

• Mitacs Globalink Research Internship (2023)

Karthik Sriram (Undergraduate summer student, 2023)

Project: Berry phase characterization of quantum materials

Materials in which the valence and the conduction bands cross at a single point are called Weyl semimetals, and the electrons show linear energy dispersion with a well-distinguished chirality. In this project, our goal is to predict and characterize the Weyl semimetals using the Density Functional Theory. We have developed the WloopPHI code to characterize the Weyl nodes and to predict the Weyl semimetals we chose the kagome lattice because it is the most fundamental model for exotic topological states in condense matter physics.

Publications:

• "WloopPHI: A tool for ab initio characterization of Weyl semimetals" Comp. Phys. Commun. 270, 108147 (2022)
• "Band alignment of monolayer CaP₃, CaAs₃, BaAs₃ and the role of p-d orbital interactions in the formation of conduction band minima" Phys. Chem. Chem. Phys. 23, 7418 (2021)

Himanshu Saini (Master student, 2022-2023; PhD student, 2019-2022)

Project: Unconventional energy storage mechanism in ZnMn₂O₄ with aqueous electrolyte

Zinc-ion batteries have gained significant research focus due to their being a safer (i.e., aqueous electrolytes) and cost-effective alternative to Lithium-ion batteries. The analysis of compatible cathode materials and a better understanding of the co-intercalation mechanism of Hydrogen ions is the goal of this project. Various structures of Manganese Dioxide cathodes will be studied. The theoretical proton placement will be modelled using density functional theory (DFT) to determine the energetic feasibility of the structure. This will then be experimentally proven with Nuclear Magnetic Resonance through a collaborative effort with the Goward team in the Chemistry department.

Larissa Grigat (Undergraduate thesis student, 2021-2022)

Project: Photonic and electronic properties of 2D materials

Two-dimensional materials like graphene, transition metal dichalcogenides and black phosphorus have tunable, layer-dependent electronic and optical properties, which makes them promising candidates for next-generation optoelectronic devices like transistors or photodetectors. We currently investigate the band alignment of newly predicted 2D materials for the purpose of 2D-heterojunction design using GW theory.

Publications/presentations:

• "Benchmarking exchange-correlation potentials with the mstar60 dataset: Importance of the nonlocal exchange potential for effective mass calculations in semiconductors" Phys. Rev. B 106, 045204 (2022)
• "WloopPHI: A tool for ab initio characterization of Weyl semimetals" Comp. Phys. Commun. 270, 108147 (2022)
• "Band alignment of monolayer CaP₃, CaAs₃, BaAs₃ and the role of p-d orbital interactions in the formation of conduction band minima" Phys. Chem. Chem. Phys. 23, 7418 (2021)
• "Exploration of the bright and dark exciton landscape and fine structure of MoS₂ using G₀W₀-BSE" Phys. Rev. B 100, 125413 (2019)
• "Pressure dependence of direct optical transitions in ReS₂ and ReSe₂" NPJ 2D Mater. Appl. 3, 20 (2019)
• North American Materials Colloquium Series (online link, February, 2021)
• BerkeleyGW workshop and conference (Oakland, California, June 2019)
• MRS Spring Meeting (Phoenix, Arizona, April 2019)

Awards:

• Best student presentation award in 2D materials symposium at MRS Spring Meeting (2019)
• Dante Cosma Graduate Memorial Scholarship (2019-2020)
• Student travel award MRS Spring Meeting (2019)
• Engineering Graduate Society's Travel Award (2019)

Magdalena Laurien (PhD Student, 2018-2021)

Project: Screening of cathode materials for aqueous Zn-ion rechargeable batteries

Aqueous Zn-ion rechargeable batteries are garnering significant attention as robust large-scale energy storage devices. The major bottleneck on the realization of Zn-ion batteries is the cathode - with current cathodes lacking either in the discharge potential or in the cycling capabilities. In this project, we screen candidate cathode materials using DFT on the basis of the stability of cathode upon intercalation and the resulting intercalation potential thereby accelerating materials discovery for better cathode materials.

Awards:

• Mitacs Globalink Research Internship (2021)

Publications:

• "Computational screening of cathode materials for Zn-ion rechargeable batteries" arXiv:2212.05396 [cond-mat.mtrl-sci] (2022)
• "Electrochemical stability of ZnMn₂O₄: Understanding Zn-ion rechargeable battery capacity and degradation" J. Phys. Chem. C 126, 10957 (2022)

Sriram Anand (Undergraduate summer student, 2021)

Project: Photovoltaic materials with polarization texture

Perovskite solar cells are one kind of very promising photovoltaics. The power conversion efficiency of perovskite solar cells are around 22%. Moreover, cheap to produce and easy to fabricate are another advantages. However, the stability of perovskite solar cells is one big challenge. Instability of perovskite solar cells shows in the form of decomposition of light-harvesting active perovskite layer. Our project is focused on improving instability of this perovskite structure. Currently, we proposed one new mechanism which can explain the instability of perovskite structure. And our next work will focus on finding some new perovskite materials which are stable and suitable for photovoltaics.

Publications/presentations:

• "Electronic properties of Pb-I deficient lead halide perovskites" J. Chem. Phys. 151, 234704 (2019)
• "Stability of aziridinium lead iodide perovskite: ring strain and water vulnerability" arXiv:1908.10462 [cond-mat.mtrl-sci] (2019)
• "Unraveling the water degradation mechanism of CH₃NH₃PbI₃" J. Phys. Chem. C 123, 19385 (2019)
• "Structural dynamics in hybrid halide perovskites: Bulk Rashba splitting, spin texture, and carrier localization" Phys. Rev. Materials 2, 114604 (2018)
• "Aziridinium lead iodide: a stable, low bandgap hybrid halide perovskite for photovoltaics" J. Phys. Chem. Lett. 9, 874 (2018)
• "Ionization energy as a stability criterion for halide perovskites" J. Phys. Chem. C 121, 11977 (2017)
• "Thermodynamic origin of instability in hybrid halide perovskites" Scientific Reports 6, 37654 (2016)
• MRS Spring Meeting (Phoenix, Arizona, April 2018)
• MRS Spring Meeting (Phoenix, Arizona, April 2017)
• Canadian Association of Physics Congress (Ottawa, June 2016)
• 28th Canadian Materials Science Conference (Hamilton, June 2016)
• 23th International Wien2k Workshop (Hamilton, June 2016)

Awards:

• Dante Cosma Graduate Memorial Scholarship (2017-2018)
• Academic Excelence Graduate Dean's Scholarship (2016)
• Academic Excelence Graduate Dean's Entrance Scholarship (2015)

Chao Zheng (PhD Student, 2015-2019)

Project: Surface modification and functionalization of nanoparticles by organic ligands: Identification of adsorption mechanisms from combined DFT and FTIR studies

Mn₃O₄ has become an important material in the development of energy storage systems. It is used in supercapacitors with high power density, long cycle life and low environmental effect. It is also known to be an active catalyst for decomposition of waste gases such as NO_x. These applications require a high surface area which can be attained by synthesis of Mn₃O₄ powder of nanometer size. Many important techniques for inorganic particle synthesis are based on aqueous processing. We are investigating the coordination modes of known organic molecules used to prevent agglomeration of nanoparticles during synthesis, onto Mn₃O₄ surface using DFT in conjunction with FTIR. We use normal mode analysis for gaining better understanding of vibration spectra. This work can aid to enhance the efficiency of liquid phase synthesis process. (Collaboration with Igor Zhitomirsky, McMaster University)

Another aspect of Divyanshu's research is modelling of planar defects in semiconductor nanowires and assessment of their impact on electronic structure, optical properties and charge transport. (Collaboration with Ray LaPierre, McMaster University)

Publications/presentations:

• "Stacking defects in GaP nanowires: Electronic structure and optical properties" J. Appl. Phys. 126, 084306 (2019)
• 25th International Wien2k Workshop (Boston, June 2018)

Divyanshu Gupta (Master Student, 2017-2019)

Project: Stability of aziridinium lead iodide perovskite

Recently, an aziridinium lead iodide perovskite was proposed as a possible solar cell absorber material. This project involves investigation of the stability of this material using a density functional theory with an emphasis on the ring strain associated with the three-membered aziridinium cation.

Publications:

• "Stability of aziridinium lead iodide perovskite: ring strain and water vulnerability" arXiv:1908.10462 [cond-mat.mtrl-sci] (2019)

Awards:

• NSERC Undergraduate Student Research Award (2019)

Kangze (Brian) Ren (Undergraduate summer student, 2019)

Project: Ion migration in halide perovskites

Artificial intelligence and deep learning rapidly proliferate into our life. The conventional von-Neumann architecture is not an ideal platform for performing this type of computations. Non-volatile memory devices with multiple resistance states can be used as a storage and computing element as they resemble the synaptic functionality of the brain. Here we use an all-inorganic perovskite CsPbBr3 as a prototype material for exploring its ionic conductivity as a mechanism for the resistive switching.

Awards:

• Mitacs Globalink Research Internship (2019)

Animesh Datta (Undergraduate summer student, 2019)

Project: Indirect excitons in 2D materials

Excitonic effects dominate the optical properties of materials, especially of low-dimensional materials such as transition metal dichalcogenides. When considering the excitonic effect, the band structure changes remarkably which can possibly even result in a change of the material's bandage type (e.g. from indirect to direct). We currently study the excitonic effect in MoS2 and other 2D-materials and explore how excitons affect their band structure.

Publications:

• "Exploration of the bright and dark exciton landscape and fine structure of MoS₂ using G₀W₀-BSE" Phys. Rev. B 100, 125413 (2019)

Awards:

• Nankai University Research Internship (2018)

Hongyu Yu (Undergraduate summer student, 2018)

Project: Rashba splitting in 2D perovskites

2D perovskites have recently attracted significant attention due to their many merits including great environmental stability, which makes them promising candidate materials for next-generation solar cells. To achieve longer carrier life and lower exciton recombination rate, the material should have a quasi-indirect band gap which arise from the Rashba splitting in both conduction and valence band edges. We currently study the Rashba splitting in several families of 2D perovskites, and explore how different organic cations, halide elements, and inorganic layer numbers can affect Rashba parameters.

Publications:

• "Rashba band splitting in two-dimensional Ruddlesden-Popper halide perovskites" (Editor's pick) J. Appl. Phys. 128, 175101 (2020)
• "Structural dynamics in hybrid halide perovskites: Bulk Rashba splitting, spin texture, and carrier localization" Phys. Rev. Materials 2, 114604 (2018)

Awards:

• Mitacs Globalink Research Internship (2018)

Shidong Yu (Undergraduate summer student, 2018)

Project: Adhesion of poly(styrene-alt-maleic acid) to hydroxyapatite and titanium oxide

Currently, hip implants are constructed with titanium, then plasma coated with hydroxyapatite (HA), a mineral also found in bone. After the implant is inserted, the bond between bone and HA becomes so strong that the HA may strip from the implant, causing the implant to fall out. The polymer Poly(Styrene-Alt-Maleic Acid) may be able to adhere to both HA and the oxide layer of titanium better than plasma coating, making it a favourable alternative to the HA coating used in the past. By virtually modelling these interactions at the molecular level and calculating the change in surface energy at the interface, we are able to determine the favourability of the polymer to adhere to HA and titanium oxide. Should the bonds be both favourable and stronger than the HA plasma coating, then our research could change the way implants are constructed.

Publications/presentations:

• "Adsorption of maleic acid on the surface of hydroxyapatite and TiO₂: a pathway toward biomaterial composites" ACS Appl. Mater. Interfaces 10, 24382 (2018)
• TMS 2018 Annual Meeting and Exhibition (Phoenix, Arizona, 2018)

Mitchell Albert (Undergraduate Research Assistant 2017-2018)

Project: Effect of compositional disorder on performance of III-V semiconductor alloys in telecommunication applications

Disorder due to mixing of isotropic elements in III-V semiconductors is rarely discussed. Developing methods to study this disorder and predict future disorder is my main interest. By understanding the disorder introduced into a system we will gain greater understanding in engineering more efficient gain materials. We have already determined a unique statistical approach in quantifying electron localization in a material for WIEN2k - which is able to capture the disorder introduced. However, the ability to predict the amount of disorder in the system is currently under study. Currently, we hypothesize the disorder to have effect on the recombination efficiency of the system in both recombination rate and electron mobility.

Publications/presentations:

• "Alloying strategy for two-dimensional GaN optical emitters" Phys. Rev. B 96, 155209 (2017)
• "Localization of electronic states in III-V semiconductor alloys: a comparative study" Phys. Rev. Applied 121, 11977 (2017)
• 59th Electronic Materials Conference (South Bend, Indiana, July 2017)
• Canadian Association of Physics Congress (Ottawa, June 2016)
• 28th Canadian Materials Science Conference (Hamilton, June 2016)
• 23th International Wien2k Workshop (Hamilton, June 2016)

Awards:

• Ontario Graduate Scholarship (2016-2017)
• 2nd Place Poster in the Division of Condensed Matter and Materials Physics at the Canadian Association of Physics Congress (2016)

Christopher Pashartis (Master Student, 2015-2017)

Project: Finite element modelling of piezoelectric transducers for ultrasonic medical imaging

Piezoelectric materials are essential components for various applications; specifically, in medicine. In hospital ultrasound systems, the essential component to produce ultrasound waves utilizes the piezoelectric effect. This phenomenon is known to convert electric energy to mechanical energy or vice versa. My role was to investigate the behavior of transducer under different loading and boundary conditions. By developing 3D models and using the simulation feature of ANSYS, I was able to analyze the various acoustic powers that would be generated at different frequencies.

Nitesh Mistry (Undergraduate Research Assistant, 2016-2017)

Project: Multiscale material simulation in modelling of solar cell performance

Taking a deeper look at the material design aspect of a simple Silicon solar cell. Material design for solar cells needs to focus on optimizing the material properties in order to attain the most efficient cells. Initially, using data gathered from First Principle calculations (DFT), devices can be simulated with great accuracy. Focusing on the effects of parameters such as The parameters studied were the following: Absorption, Bandgap, Lifetime of Carriers, Auger Recombination, and Electron and Hole mobility effect the efficiency of a simple Si solar cell.

Lina Qamar (Undergraduate Research Assistant, 2016)

Project: Enhanced chemical stability of mixed halide perovskite photovoltaics

With the search for higher solar cell efficiencies and lower manufacturing costs scientists and engineers have come up with some ingenious materials and technologies. One of such materials is the methylammonium lead iodide perovskite that has gained significant attention in the past 5 years. My efforts this summer (2015) were directed at investigating the stability of the material and possibly providing some new changes to the material itself. Manipluation of the cation within crystal can be examined computational fairly quickly where as the same experiments would be far more strenuous. The crystallographic and stability calculations were done using Abinit while the band structures were created using Wien2k.

Publications:

• "Thermodynamic origin of instability in hybrid halide perovskites" Scientific Reports 6, 37654 (2016)

Awards:

• NSERC Undergraduate Student Research Award (2015)

Eric Tenuta (Undergraduate Research Assistant, 2015-2016)

Project: Electronic structure of disordered solids

fold2Bloch is a new tool for studying the electronic structure of disordered solids. It enables "unfolding" of the band structure of supercells back to its conventional (Bloch) representation. For example, it can be useful for visualizing the band structure of compound alloys and quantify the extent of disorder. The software is able to interface with Wien2k all-electron DFT package. The interface with abinit is in progress and expected to be released by the end of 2014.

Publications/presentations:

• "Recent developments in the ABINIT software package" Computer Physics Communications 205, 106 (2016)
• "Unfolding the band structure of disordered solids: from bound states to high-mobility Kane fermions" Phys. Rev. B 90, 115202 (2014)
• Abinit Developper workshop (Liege, Belgium, 2015)

Awards:

• ELEKTA Student Travel Award (TBRRI, 2015)

Anton Bokhanchuk (Research Assistant, 2014-2015)

Project: Molecular mechanisms of biocompatibility of syntectic materials

Biomaterials are widely used as an interface between implants and tissue in order to prevent the failure as a result of immune rejection. Implant rejection requires additional surgical intervention and, ultimately, increases health cost as well as recovery time. Within a few hours after implantation, the implant surface is covered with host proteins, which determines further immune response and, eventually, the biocompatibility of a given material. In this project we focus on modeling the interaction between artificial surfaces (such as graphene) and plasma proteins at the atomistic level taking into account the explicit biological environment. Our findings provide a foundation for development of novel coatings for implants with improved biocompatibility and bioadhesion.

Publications/presentations:

• "Molecular dynamics of Fibrinogen adsorption onto Graphene, but not onto Poly(ethylene glycol) surface, increases exposure of recognition sites that trigger immune response" J. Chem. Inf. Model. 56, 706 (2016)
• "An atomic charge model for graphene oxide for exploring its bioadhesive properties in explicit water" J. Chem. Phys. 141, 044705 (2014)
• "Binding of solvated peptide (EPLQLKM) with a graphene sheet via simulated coarse-grained approach" J. Chem. Phys. 140, 204901 (2014)
• "Favorable adsorption of capped amino acids on graphene substrate driven by desolvation effect" J. Chem. Phys. 139, 174711 (2013)
• Faraday Discussion 175: Physical chemistry of functianalised biomedical nanoparticles (Bristol, UK, 2014)
• Canada Association of Physics Congress (Montreal, May 2013)

Awards:

• ELEKTA Student Travel Award (TBRRI, 2014)
• Best-of-the-best poster presentation at Research & Innovation Week (Lakehead University, 2014)
• Ontario Graduate Scholarship 2013-2014

Co-supervisor: Dr. Wely B. Floriano

Nadiya Dragneva (PhD Biotechnology student, 2012-2015)

Project: Bioadhesive properties of polar surfaces

An increase in the use of artificial medical implants has created a need for the development of bio-compatible and bio-adhesive materials. Various properties of promising materials (such as graphene-based nanomaterials) can be analyzed through molecular dynamics software. This summer, I assisted in developing and analyzing a molecular model of a graphene-oxide surface. I gained valuable experience in working with molecular modeling software, various Matlab applications, super-computing, and many other forms of data analysis.

Publications:

• "An atomic charge model for graphene oxide for exploring its bioadhesive properties in explicit water" J. Chem. Phys. 141, 044705 (2014)
• "Favorable adsorption of capped amino acids on graphene substrate driven by desolvation effect" J. Chem. Phys. 139, 174711 (2013)

Awards:

• NSERC Undergraduate Student Research Award (2014)
• NSERC Undergraduate Student Research Award (2013)

Co-supervisor: Dr. Wely B. Floriano

Dennis Stauffer (Undergraduate Research Assistant, 2013-2014)

Project: Computer simulation of functional materials for therapeutic ultrasound applications.

The performance of ultrasonic transducers for high-power applications, such as high-intensity focused ultrasound, is affected by a dielectric dissipation that results in a risk of thermal runaway. The aim of this thesis is twofold: to establish a microscopic origin of the dielectric loss in ferroelectric materials and, secondly, to propose approaches for its reduction. The modern theory of polarization was combined with a first principle electronic structure method in order to determine relevant material properties. Our study of a ferroelectric switching at the microscopic level has lead to the development of a new method for driving ferroelectric crystals with a minimized energy loss. The anticipated implications of this work are a reduction of the risk of thermal damage to the tissue at the interface with the transducer, an improvement to the working stability of the transducer and further miniaturization of ultrasonic actuators with limited access to thermal sink. Sheikh was actively involved in developing a software "BerryPI" - an additional software package for WIEN2k density-functional theory code, which enables calculation of polarization related properties of crystalline solids using Modern theory of polarization.

Publications/presentations:

• "Unfolding the band structure of disordered solids: from bound states to high-mobility Kane fermions" Phys. Rev. B 90, 115202 (2014)
• "First-principle modelling of the ferroelectric switching in BaTiO3: concurrent switching vs domain wall motion" Modelling Simul. Mater. Sci. Eng. 22, 055014 (2014)
• "Marble game with optimal ferroelectric switching" J. Phys.: Condens. Matter 26, 135901 (2014)
• "BerryPI: A software for studying polarization of crystalline solids with WIEN2k density functional all-electron package" Comp. Phys. Commun. 184, 647 (2013)
• Canada Association of Physics Congress (Montreal, May 2013)
• Theory Canada conference (Lethbridge, June 2012)
• Canada Association of Physics Congress (Calgary, June 2012)

Co-supervisor: Dr. Samuel Pichardo

Email:

Sheikh Jamil Ahmed (MSc Physics student, 2011-2013)

Project: Marble game with ferroelectric switching

Ferroelectric materials yield an abundance of applications largely due to their piezoelectric property. One such application is High-Intensity Focused Ultrasound (HIFU), which offers a minimally invasive method to destroy cancerous tissue, assist in drug delivery, and many other medical functions. Over the course of the summer I engaged in a variety of tasks all leading to the discovery of the potential profile for ferroelectric materials. With my background in computer science I was able to create several file manipulation and parsing programs to accelerate the process. Additionally, I created many real-time interactive simulations to better visualize what was occurring at the atomic level of these materials. I have gained an immense amount of knowledge in the fields of crystallography, mathematics, and computer graphics throughout the summer, and I am forever grateful for the opportunities that the Thunder Bay Regional Research Institute has presented.

Publications:

• "Marble game with optimal ferroelectric switching" J. Phys.: Condens. Matter 26, 135901 (2014)

Awards: NOHFC Youth Internship and Co-Op Scolarship

Co-supervisors: Drs. Samuel Pichardo and Laura Curiel

Email:

Jeremy Cole (Summer co-op student, 2013)

Project: Microscopic modelling of high-field transport in amorphous selenium.

Electrons avalanche multiplication has lead to the development of avalanche-based photodiodes. The latter have found a wide variety of applications in the electronics market including laser range finders, TV camera tubes, fiber optic telecommunications and potential use in medical imaging detectors. Recently, there has been a growing interest to use amorphous semiconductors instead of crystalline since amorphous production is economically more favorable than crystalline. Selenium is the only material that has been reported clearly to feature avalanche phenomenon in the amorphous phase at a practical electric field. My intriguing project is an attempt to understand the physics behind the uniqueness of amorphous Selenium in representing the impact ionization process. The latter was undertaken by first principle studying of the electronic structure and the electron-phonon interaction in Selenium.

Publications/presentations:

• "First-principle prediction of single-carrier avalanche multiplication in chalcopyrite semiconductors" J. Appl. Phys. 113, 203104 (2013)
• "Impact ionization threshold energy of trigonal Selenium: an ab initio study" Can. J. Physics 91, 483 (2013)
• "Modeling the radiation ionization energy and energy resolution of trigonal and amorphous selenium from first principles" J. Phys.: Condens. Matter 24, 455502 (2012)
• "Interaction of hot carriers with optical phonons in Selenium" J. Non-Cryst. Solids 358, 2434 (2012)
• Theory Canada conference (Lethbridge, June 2012)
• Canada Association of Physics Congress (Calgary, June 2012)

Email:

Ali Darbandi (MSc Physics student 2010-2012)

Project: Modelling the electron-hole pair generation by ionizing radiation in selenium.

Selenium is an amorphous (disordered) material used in medical imaging applications mainly as an x-ray detector. Though it has many applications, little is know about the structure and intrinsic properties of selenium. During my term here, I was involved in modelling the electron-hole-pair creation in selenium, as well as creating a rudimentary model for its disordered structure. My work consisted mainly of the development and implementation of mathematical algorithms in MatLab, as well as high-performance computing using abinit software. From this work, not only did I learn an incredible amount, but relevant intrinsic values for the electron-hole-pair creation energy and Fano factor in selenium were determined, while the work on the amorphous structure is still ongoing. I am very grateful for the knowledge I have gained and the opportunities that the Thunder Bay Regional Research Institute has offered me, it was a wonderful way to spend a summer.

Publications:

• "Modeling the radiation ionization energy and energy resolution of trigonal and amorphous selenium from first principles" J. Phys.: Condens. Matter 24, 455502 (2012)

Awards: 2nd prize winner - Summer Student Presentations Competition 2012

Alise Devoie (Summer co-op student, 2012)

Project: Computer simulation of functional materials for therapeutic ultrasound applications.

This summer I worked on the design of piezoelectric materials for therapeutic ultrasound focussing on increasing the efficiency of the piezoelectric ceramic in an ultrasound transducer in order to improve High Intensity Focussed Ultrasound treatment. I was able to calculate multiple elastic constants for commonly studied compounds in order to show that density functional theory can be used for accurate calculations. I was also able to gain hands on experience by performing two experiments in order to measure the efficiency of ultrasound transducers. I liked how I could do both theoretical calculations and hands on experiments in the lab. I have gained a lot of knowledge and experience through this summer research project and I am very thankful to have been a part of the Thunder Bay Regional Research Institute this summer.

Awards: NSERC Undergraduate Student Research Award

Co-supervisor: Dr. Laura Curiel

Kaci Karter (Summer student, 2012)

Project: Recombination of geminate charge carriers in the presence of disorder

The problem of the dissociation of geminate electron-hole pairs and the problem of injection of electrons into a semiconductor from a metallic contact are among the most often discussed topics in the field of disordered systems, particularly amorphous and organic disordered materials. The central question in both cases is how charge carriers escape from the Coulomb potential well created by their counterparts via a series of noncoherent hopping transitions between spatially localized states or in a diffusion manner. It has been shown that an energetic disorder, which arises from structural imperfections, significantly affects the dissociation probability. Recently an analytical solution was obtained for the specified problem in the 1D case. The goal of this project was to extend the model to higher dimensions (2D and 3D), which makes the model more relevant to experiments. A solution of the dissociation and injection problems is of vital importance for the physics of molecular solar cells, organic light emitting diodes, polymer field effect transistors, and other optoelectronic devices.

Publications:

• "Modeling the radiation ionization energy and energy resolution of trigonal and amorphous selenium from first principles" J. Phys.: Condens. Matter 24, 455502 (2012)

Awards: 2nd prize winner - Summer Student Presentations Competition 2011; NSERC Undergraduate Student Research Award

Olivia Di Matteo (Summer student, 2011)

Project: Modelling the avalanche multiplication in disordered semiconductors

Andrew significantly advanced the accuracy and simplified mathematically the lucky-drift model model of avalanche multiplication for disordered semiconductors.

Publications:

• "Generalized lucky-drift model for impact ionization in semiconductors with disorder" J. Phys.-Cond. Matter 23, 055802 (2011)
• "Bulk Properties of alpha-PbO from first-principle self-consistent calculations" AIP Conference Proceedings 1368, 85 (2011)

Andrew Potvin (Summer student, 2010)

Project: Modelling the avalanche multiplication in disordered semiconductors

Daniel made a key contribution to uncovering the physics behind uniqueness of avalanche multiplication in amorphous selenium, in particular relating this phenomenon to features of the electronic structure.

Publications:

• "Generalized lucky-drift model for impact ionization in semiconductors with disorder" J. Phys.-Cond. Matter 23, 055802 (2011)
• "Lone-pair states as a key to understanding impact ionization in chalcogenide semiconductors" J. Phys.-Cond. Matter 22, 355803 (2010)

Daniel Laughton (Summer student, 2009)