University of Minnesota
School of Physics & Astronomy
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Eric Ganz

PAN 319 (office), 624-2386
ganzx001 @ umn.edu • curriculum vitae

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I'm a solid-state physicist with interests in computational studies of materials. Currently I am studying new classes of porous materials called metal organic frameworks, as well as two-dimensional materials.

Member of Minnesota Supercomputing Institute

Summary of Interests
Calculations of the properties of novel Materials

About My Work

I am interested in modeling the properties of novel materials. This can include 2 dimensional materials, as well as porous frameworks materials such as metal organic frameworks and covalent organic framework materials. These new porous materials are built from molecular building blocks, and so can be designed to provide a very wide range of capabilities.

Just out:

The Initial Stages of Melting of Graphene Between 4000 K and 6000 K
http://pubs.rsc.org/en/content/articlelanding/2017/cp/c6cp06940a#!divAbstract

Graphene and its analogues have some of the highest predicted melting points of any materials. Previous work estimated the melting temperature for freestanding graphene to be a remarkable 4510 K. However, this work relied on theoretical methods that do not accurately account for the role of bond breaking or complex bonding configurations in the melting process. Furthermore, experiments to verify these high melting points have been challenging. Practical applications of graphene and carbon nanotubes at high temperatures will require a detailed understanding of the behavior of these materials under these conditions. Therefore, we have used reliable ab initio molecular dynamics calculations to study the initial stages of melting of freestanding graphene monolayers between 4000 and 6000 K. To accommodate large defects, and for improved accuracy, we used a large 10 × 10 periodic unit cell. We find that the system can be heated up to 4500 K for 18 ps without melting, and 3-rings and short lived broken bonds (10-rings) are observed. At 4500 K, the system appears to be in a quasi-2D liquid state. At 5000 K, the system is starting to melt. During the 20 ps simulation, diffusion events are observed, leading to the creation of a 5775 defect. We calculate accurate excitation energies for these configurations, and the pair correlation function is presented. The modified Lindemann criterion was calculated. Graphene and nanotubes together with other proposed high melting point materials would be interesting candidates for experimental tests of melting in the weightless environment of space.

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Computational Study of Quasi-2D Liquid State in Free Standing Platinum, Silver, Gold, and Copper Monolayers
LM Yang, AB Ganz, M Dornfeld, E Ganz
Condensed Matter 1 (1), 1

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Abstract: Recently, freestanding atomically thick Fe metal patches up to 10 atoms wide have been fabricated experimentally in tiny pores in graphene. This concept can be extended conceptually to extended freestanding monolayers. We have therefore performed ab initio molecular dynamics simulations to evaluate the early melting stages of platinum, silver, gold, and copper freestanding metal monolayers. Our calculations show that all four freestanding monolayers will form quasi-2D liquid layers with significant out-of-plane motion and diffusion in the plane. Remarkably, we observe a 4% reduction in the Pt most likely bond length as the system enters the liquid state at 2400 K (and a lower effective spring constant), compared to the system at 1200 and 1800 K. We attribute this to the reduced average number of bonds per atom in the Pt liquid state. These liquid states are found at temperatures of 2400 K, 1050 K, 1600 K, and 1400 K for platinum, silver, gold, and copper respectively. The pair correlation function drops in the liquid state, while the bond orientation order parameter is reduced to a lesser degree.

We also recently released a study on the freestanding 2-D silver monolayer.

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Four Decades of the Chemistry of Planar Hypercoordinate Compounds
The emergence and growth of the field of planar hypercoordinate chemistry over more than four decades is reviewed. Although the paradigm of planar tetracoordinate carbon (ptC) was considered implausible for a century after 1874, examples were then predicted computationally and realized experimentally. Both electronic and mechanical (e.g., small rings and cages) effects stabilize such unusual bonding arrangements. The evolution of such planar configurations from small molecules to clusters, to nanospecies and to bulk solids is delineated.

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Two-Dimensional Cu2Si Monolayer with Planar Hexacoordinate Copper and Silicon Bonding
Two-dimensional materials with planar hypercoordinate motifs are extremely rare due to the difficulty in stabilizing the planar hypercoordinate configurations in extended systems. We predict a novel Cu2Si 2D monolayer featuring planar hexacoordinate copper and planar hexacoordinate silicon. This system has been studied with density functional theory, including molecular dynamics simulations and electronic structure calculations. Bond order analysis and partitioning reveals 4c–2e σ bonds that stabilize the two-dimensional structure. We find that the system is quite stable during short annealing simulations up to 900 K, and predict that it is a nonmagnetic metal. This work opens up a new branch of hypercoordinate two-dimensional materials for study.

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The way that mussels stick to rocks is inspiring new biomimetic adhesives that could be non-toxic and potentially used internally. Credit: Shaith/iStock/Thinkstock

1. Mussels have a remarkable ability to bond to solid surfaces under water. From a microscopic perspective, the first step of this process is the adsorption of dopa molecules to the solid surface. In fact, it is the catechol part of the dopa molecule that is interacting with the surface. These molecules are able to make reversible bonds to a wide range of materials, even underwater. We uncover the nature of this competitive absorption by atomic scale modeling of water and catechol adsorbed at the geminal (001) silica surface using density functional theory calculations. We find that catechol molecules displace preadsorbed water molecules and bond directly on the silica surface. Using molecular dynamics simulations, we observe this process in detail. We also calculate the interaction force as a function of distance, and observe a maximum of 0.5 nN of attraction. The catechol has a binding energy of 23 kcal/mol onto the silica surface with adsorbed water molecules. Here is the link to the press release for this paper: External Link

Energetics and thermodynamics of the initial stages of hydrogen storage by spillover on prototypical Metal-Organic Framework (MOF) and Covalent-Organic Framework (COF) materials. For many years, experimenters have struggled to reproduce and extend the original spillover results that were carried out on IRMOF-1. For pure IRMOF-1 it has been suggested (based on calculations of molecular fragments) that there is an enthalpy barrier to the addition of the first hydrogen per benzene, and that this barrier is removed by hole doping. This explains why very specific procedures such as annealing cycles (which damage the frameworks) needed to be used in the experiments. Using density functional theory on more accurate and much more computationally expensive periodic frameworks, we do not observe this enthalpy barrier. However, we do observe that the binding energy for the first hydrogen is unfavorable and creates a kinetic barrier without hole doping. Hole doping by zinc vacancies removes this energy barrier. Therefore, hole doping by Zn vacancies or other means is still necessary for the hydrogen storage process to proceed. We also see that the direction of the hydrogen sorption reaction as a function of hydrogen gas pressure can be predicted by the change in Gibbs free energy.
Another challenge for the use of for the use of IRMOF-1 in real-world hydrogen storage situations is that the material degrades upon exposure to small amounts of water vapor. Therefore more durable materials such as water resistant metal organic frameworks, or covalent organic frameworks would be much more desirable for these applications. Unfortunately, as mentioned above, it has not been possible to achieve significant hydrogen storage in either of these cases. Now, our calculations may explain why it has been difficult to achieve significant hydrogen spillover on COF materials. For COF-5, we find that the energy barrier is not resolved by doping, and therefore hydrogen spillover will not proceed unless some new sample preparation technique is developed.

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COF-5 model showing top view of unit cell.
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The newly synthesized Zr metal-organic frameworks (UiO-66, 67, 68) as well as analogues substituting Ti and Hf for Zr, are explored using density functional theory calculations. Crystal structure, phase stability, bulk modulus, electronic structure, formation enthalpies, powder X-ray diffraction, chemical bonding, and optical properties are studied. We find bulk moduli of 36.6, 22.1, 14.8 GPa for UiO-66, -67, and -68 respectively. As the linkers are extended, the bulk modulus drops. The band gaps range from 2.9 to 4.1 eV. The compounds have similar electronic structure properties. Experimental PXRD patterns compare well with simulation. The large formation enthalpies (40 to 90 kJ/mol) for the series indicate high stability. This is consistent with the fact that these materials have very high decomposition temperatures. A detailed analysis of chemical bonding is carried out. Potential applications for these new materials include organic semiconducting devices such as field-effect transistors, solar cells, and organic light-emitting devices. We hope that the present study will stimulate research in UiO-based photocatalysis and will open new perspectives for the development of photocatalysts for water splitting and CO2 reduction. The large surface areas also make these materials good candidates for gas adsorption, storage, and separation.

My old webpage on scanning tunneling microscopy is here: Internal Link
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Advisees and Collaborators

Li-Ming Yang

Selected Publications

Eric Ganz, Ariel B. Ganz, Li-Ming Yang and Matthew Dornfeld , The initial stages of melting of graphene between 4000 K and 6000 K, Phys. Chem. Chem. Phys. [abstract]

Li-Ming Yang, Ariel B. Ganz, Matthew Dornfeld and Eric Ganz, Computational Study of Quasi-2D Liquid State in Free Standing Platinum, Silver, Gold, and Copper Monolayers, Condensed Matter [abstract] [download condensedmatter-01-00001(1).pdf]

Li-Ming Yang, Eric Ganz, Zhongfang Chen, Zhi-Xiang Wang and Paul von Ragué Schleyer, Four Decades of the Chemistry of Planar Hypercoordinate Compounds, Angewandte Chemie International Edition [abstract]

Yang L, Yang V, Popov I A, Boldyrev A I, Heine T, Frauenheim T, Ganz E., Two-Dimensional Cu2Si Monolayer with Planar Hexacoordinate Copper and Silicon Bonding, Journal of the American Chemical Society [abstract]

Shabeer Ahmad Mian, Li-Ming Yang, Leton Chandra Saha, Ejaz Ahmed, Ajmal Muhammad, Eric Ganz, A Fundamental Understanding of Catechol and Water Adsorption on a Hydrophilic Silica Surface: Exploring the Underwater Adhesion Mechanism of Mussels on an Atomic Scale, Langmuir [abstract]

Li-Ming Yang, Eric D Ganz, Stian Svelle and Mats Tilset , Computational Exploration of Newly Synthesized Zirconium Metal-Organic Frameworks UiO-66, 67, 68 and Analogues, J. Mater. Chem. C [abstract]

L.-M. Yang, G.-Y. Fang, J. Ma, E. Ganz, and S.S. Han, Band Gap Engineering of MOF-5 by Atom Substitution, J. Mol. Chem. C

E. Ganz* and M. Dornfeld, Energetics and Thermodynamics of the Initial Stages of Hydrogen Storage by Spillover on Prototypical Metal-Organic Framework and Covalent-Organic Framework Materials, J. Phys. Chem. C [abstract]

Eric Ganz and Matthew Dornfeld, Storage Capacity of Metal-Organic and Covalent-Organic Frameworks by Hydrogen Spillover, J. Phys. Chem. C. 116, 3661 [abstract] [download jp2106154.pdf]

Mayur Suri, Matthew Dornfeld, and Eric Ganz, Calculation of hydrogen storage capacity of metal-organic and covalentorganic frameworks by spillover, [abstract] [download JCPSA613117174703_1.pdf]

T. Sagara and E. Ganz, “Calculations of Dihydrogen Binding to Doped Carbon Nanostructures”, J. Phys. Chem. C. (2008)

T. Sagara, J. Ortony, and E. Ganz, New isoreticular metal-organic framework materials for high hydrogen storage capacity, Journal of Chemical Physics [abstract] [download C:\Users\Eric\Documents\Papers\Ganz\New isoreticular metal-o]

Education

B.S., Physics, Stanford University, 1982.
Ph.D., Physics, University of California, Berkeley, 1988.