Yu wins Humboldt Fellowship for Postdoctoral Researchers

Dr. Yonggang Yu, former student and currently a post-doc in the Wenzcovitch Group, has been awarded the Humboldt Fellowship for Postdoctoral Researchers by the Alexander von Humboldt Foundation in the Federal Republic of Germany. He will be working at the University of Frankfurt’s Institute of Geosciences in the laboratory of Prof. Bjoern Winkler. Yonggang will work on phase equilibria and physical properties of garnet and perovskite systems by exploring Al and Fe effects on the mineral aggregate under high pressure and high temperature conditions of the Earth's transition zone and top of lower mantle. His research intends to reveal more details and unknowns of the Earth's transition zone and enrich understanding of the mineralogy of the mantle. Yonggang's Ph.D. thesis was titled "First Principles Investigation of Mantle Minerals", for which he was given the 2009 “Mineral and Rock Physics Graduate Research Award" given annually by the American Geophysical Union to promising young scientists for outstanding contributions achieved during their Ph.D. research.

Spin-State Crossover and Hyperfine Interactions of Ferric Iron in MgSiO3 Perovskite

"Spin-State Crossover and Hyperfine Interactions of Ferric Iron in MgSiO3 Perovskite", Han Hsu, Peter Blaha, Matteo Cococcioni, and Renata M. Wentzcovitch, Physical Review Letters, 106, 118501 (2011) (DOI: 10.1103/PhysRevLett.106.118501)

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• Physics Today: "Electron spins in Earth's mantle", March 31, 2011
  

  When a transition-metal compound is subject to high pressure, its electronic spin state can change, which in turn can change the compound's material properties. That spin-state crossover is of geophysical relevance because of the iron-bearing minerals in Earth's lower mantle. But the most abundant mantle mineral—Fe-bearing magnesium silicate perovskite (Pv)—is a challenge to study. MORE...

• Physics Today: "Calculations clarify the role of minerals' electron spins in Earth's mantle", Phys. Today 64, 5, 12 (2011)
  

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Theoretical and Computational Methods in Mineral Physics: Geophysical Applications
edited by Renata Wentzcovitch and Lars Stixrude

This book presents a set of review articles offering an overview of contemporary research in computational mineral physics. Fundamental methods are discussed and important applications are illustrated. The opening chapter by John Perdew and Adrienn Ruzhinszky discusses the motivation, history, and expressions of Kohn-Sham Density Functional Theory (DFT) and approximations for exchange and correlation. This is the established framework for investigation of a condensed matter system’s ground state electronic density and energy. It also discusses the recent trend to design higher-level semi-local functionals, with solid state applications in mind. It presents arguments in favor of semi-local approximations for condensed matter and discusses problematic cases where fully non-local approximations are needed. MORE...

Núñez-Valdez wins AGU Outstanding Student Paper Award
"Fundamentals of elasticity for Fe-bearing forsterite" expands understanding of effects of chemistry on seismic velocities

Maribel Núñez-Valdez, a PhD candidate in Physics at UMN, won the 2009 Outstanding Student Paper Award of the Mineral and Rock Physics Focus Group (MRP) of the American Geophysical Union (AGU) Fall Meeting. Núñez-Valdez's work involved first-principles calculations of elastic properties of iron-bearing forsterite, the most abundant phase in the Earth’s upper mantle. These predictions helped shed light on the role of chemical composition in seismic velocities. Maribel is currently in the last stage of her PhD. Prof. Renata Wentzcovitch served as her advisor.

Yu wins 2009 AGU Graduate Research Award
"Structure properties and phase transitions in earth minerals: A first principles study" investigates origins and predicts magnitudes of seismic discontinuities

Dr. Yonggang Yu,, a 2008 PhD in Chemical Physics at UMN, won the 2009 Graduate Research Award of the Mineral and Rock Physics Focus Group (MRP) of the American Geophysical Union (AGU) for his PhD thesis, "Structure properties and phase transitions in earth minerals: A first principles study". His work involved first-principles calculations of thermodynamic phase boundaries in Earth-forming minerals that produce seismic velocity discontinuities in the Earth's mantle. These predictions shed light on the origins of such seismic discontinuities. Dr. Yu is now a post-doc in Geosciences at Virginia Tech. Prof. Renata Wentzcovitch served as his advisor at UMN.

Body-Centered Tetragonal C4: A Viable sp3 Carbon Allotrope
"Body-Centered Tetragonal C4: A Viable sp3 Carbon Allotrope",
K. Umemoto, R.M. Wentzcovitch, S. Saito, and T. Miyake, Physical Review Letters, 104, 125504 (2010)
(DOI: 10.1103/PhysRevLett.104.125504)

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• Physical Review Focus: "Between Graphite and Diamond", October 29, 2010
  

  Pure carbon has a wide variety of atomic structures, such as diamond and graphite, but the structure created by a 2003 graphite compression experiment has been controversial. Now two teams of theorists have followed different lines of evidence to suggest that the structure involves a 3D network of four-atom rings called bct-carbon. In the 26 March Physical Review Letters, one team reported simulations that agree with the 2003 data, and in the October Physical Review B, the other team shows that the energy barrier to create bct-carbon is low enough that it could have appeared in the 2003 experiment. Researchers say the results point to the existence of a new and unexpectedly simple form of carbon. MORE...

Spin transition in Magnesiowüstite in Earth’s lower mantle
"Spin transition in Magnesiowüstite in Earth’s lower mantle",
T. Tsuchiya, R.M. Wentzcovitch, S. de Gironcoli, Physical Review Letters, 96, 198501 (2006)
(DOI: 10.1103/PhysRevLett.96.198501)

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• Eos: "Electronic Spin Transition of Iron in the Earth’s Deep Mantle", January 9, 2007
  

  Electronic spin is a quantum property of every electron, associated with its intrinsic angular momentum. The electronic structure of iron in minerals is generally such that valence electrons will more abundantly occupy different spatial orbitals and maintain the same spin than occupy the same spatial orbital and assume opposite spin, called ‘spin-paired.’ To the astonishment of mineral physicists, pressure-induced electronic spin-pairing that were predicted in iron nearly 50 years ago recently have been detected in ultrahigh-pressure experiments, MORE...

Dissociation of MgSiO₃ in the Cores of Gas Giants and Terrestrial Exoplanets
"Dissociation of MgSiO₃ in the Cores of Gas Giants and Terrestrial Exoplanets",
K. Umemoto, R. M. Wentzcovitch, and P. B. Allen, Science, 311, 983 (2006)

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• UMN press release: "U of M researcher simulates characteristics of planetary cores", February 17, 2006
  

  University of Minnesota researchers Renata Wentzcovitch and Koichiro Umemoto and Philip B. Allen of Stony Brook University have modeled the properties of rocks at the temperatures and pressures likely to exist at the cores of Jupiter, Saturn and two exoplanets far from the solar system. They show that rocks in these environments are different from those on Earth and have metallic-like electric and thermal conductivity. MORE...

• USA Today: "New planets so close and yet so far", February 21, 2006
  

  Astronomers have detected more than 150 planets orbiting nearby stars. But there may be trouble finding a planet in the "habitable zone," in which temperatures are neither too cold nor too hot for life. "But it may not be so simple," says University of Minnesota physicist Renata Wentzcovitch and colleagues in the current Science magazine. MORE...

MgSiO₃ postperovskite at D″ conditions
"MgSiO₃ postperovskite at D″ conditions",
R.M. Wentzcovitch, T. Tsuchiya, and J. Tsuchiya, PNAS, 3, 543 (2006)

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• UMN press release: "U of M researchers unlock mystery of layer encircling the Earth's core", January 30, 2006
  

  The research "tells us how to better model Earth's internal processes," said Wentzcovitch. "Proper geodynamical modeling of the Earth is necessary to get a better grasp of the dynamics of the surface. You can't fully understand Earth's surface motion without understanding how it moves inside. What's unbelievable is how well we can model Earth on a big scale." MORE...

Thompson Essential Science Indicators Names Our Article "New Hot Paper"

Our paper "Phase Transition in MgSiO3-perovskite in the Earth's Lower Mantle", has been highly cited because we reported an important theoretical discovery related to MgSiO₃ perovskite, the major Earth-forming mineral. Our findings combined with the earlier experimental findings by M. Murakami and K. Hirose at the Tokyo Institute of Technology, is the most important discovery in the field of mineral physics since 1974. Our results have extensive and interdisciplinary impact in the field of geophysics. MORE...

Virtual Laboratory for Earth and Planetary Materials

Experiments at planetary interior conditions are extremely challenging or virtually impossible. Theory may provide today and for a long time to come, the only way to obtain key information on materials properties at relevant conditions. The Virtual Laboratory for Earth and Planetary Materials , VLab funded by NSF is a consortium that promotes developments in theoretical and computation Earth and planetary material sciences.

Minnesota Daily: "University researchers head creation of virtual laboratory", November 24, 2004
The University is leading an international group of universities in developing a virtual laboratory for Earth and planetary studies with a grant from the National Science Foundation. The laboratory will help researchers study planetary materials, such as rocks, ice, iron, and gases, under conditions difficult to reproduce without a computer, principal investigator and University chemical engineering and materials science professor Renata Wentzcovitch said. MORE...

Insights on the nature of the earth's lower mantle
"Thermoelasticity of MgSiO3 perovskite: insights on the nature of the earth's lower mantle",
R. M. Wentzcovitch, B. B. Karki, M. Cococcioni, and S. de Gironcoli, Phys. Rev. Lett. 92, 018501 (2004).

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• Phys. Rev. Focus: "What is down there?", January 9, 2004
  

  Like bats using echolocation to navigate through the night, geophysicists rely on seismic waves for information on the Earth's deep interior. Almost everything known about that inaccessible region is inferred from the speed of sound waves generated by earthquakes. In the 9 January PRL, however, a team describes a calculation of the properties of the Earth's lower mantle starting from basic physics principles. The results disagree slightly with seismic data and suggest that the structure of minerals in the Earth's lower mantle is more complex than geophysicists have assumed. MORE..

Revised: January 29, 2007
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