Figure 1. Structure of ubiquitin-UIM1 complex. Ubiquitin is shown in red, while experimental structure of UIM1 is shown in blue. The lowest energy structure of UIM1 from the coarse-grained model simulation is shown in green. Computational Biophysics

We investigate energetics, structures, thermodynamics, and kinetics of biomolecules via computational tools. Of particular interest are first-principles calculations of biomolecular interactions, structure prediction of multiprotein complexes, thermodynamics, and kinetic properties of protein-protein association. We build computational tools to simulate biomolecular interactions.

Figure 1. Success of the NRL Tight-Binding Method Computational Methods

The Center supports the Office of Naval Research's Grand Challenge "Navy Materials by Design" by developing and maintaining a variety of computational tools. These include first-principles methods based on density-functional theory, specialized models for highly correlated systems, efficient tight-binding and overlapping-atom models, and simulation methods spanning multiple length scales.

Figure 1. The structures of two-dimensional Li<sub>2</sub>RuO<sub>3</sub> and three-dimensional RuO<sub>2</sub> have important consequences for their respective voltage profiles. As both the calculated and measured discharge curves show, very little Li can be incorporated into the rutile RuO<sub>2</sub> framework, while the layered host structure accomodates nearly twice as much. Energy Storage

We investigate the underlying physical and chemical principles that facilitate efficient energy storage and creation. Through computationally driven insight into the relationships between structure, composition, and performance, we evaluate materials for their usefulness as battery cathodes and anodes or as fuel cell catalysts.

Figure 1. This plot of the Fermi surface of Ag2NiO2 illustrates the effect of magnetism on transport properties. The left panel shows the spin-majority Fermi surface, and the right panel the spin-minority one. The minority surface contains fast electrons derived from Ag s and p bands, while the majority surface contains both slow electrons (central cylinder and outside edge of hexagonal network) and fast electrons (inside edge of network). Magnetic Materials and Magnetism in Semiconductors

The Center studies a broad range of magnetic materials, from hard magnetic materials to dilute magnetic semiconductors. Some of these materials form the basis of current magnetoelectronic technologies, while others -- both soft and hard magnets -- are being studied for future applications. In addition, this research focuses on semiconductors that are rendered magnetic by either intrinsic or extrinsic effects. These materials, which offer the advantages of semiconductors combined with the non-volatile properties of magnetic materials, are the materials foundation for future "spintronics" technologies.

Figure 1. Visualization of an atomistic simulation of the evolution of a grain surrounded by two other grains.  The inner grain does not rotate, in contrast to the grain surrounded by a single crystal matrix, because of frustration. Mechanical Properties

We apply computational methods including first principles, tight binding, interatomic potentials, and coupling of length scales approaches to the simulation of mechanical properties. Applications range from static calculations of quantities such as ideal strength and ductility criteria, to dynamic simulations of finite-temperature ideal strength and dynamic fracture.

Figure 1. The three relevant length scales for quantum information processing using single electron quantum dots. Quantum Information

A broad program is underway to use single-electron quantum dots in silicon for quantum information processing. A theoretical description of this system is necessarily multiscale, ranging from density functional theory at the atomic level to time-dependent model Hamiltonian calculations of many-dot systems. Optimal experimental designs to minimize decoherence will be examined.

Figure 1. The density of electron spin precession modes in an ensemble of singly charged QDs is modified by the nuclei. The black curve shows the density of modes before the nuclear induced frequency focusing due to the ensemble dispersion of electron g-factor and nuclear polarization fluctuations. The train of short optical pulses reduces the continuous density of electron spin precession modes to just three frequencies (blue). Quantum Dots

Quantum dots are a new form of matter that can be considered as "artificial atoms." They have linear discrete absorption spectra (like atoms) and photoluminescence that is tunable (by changing the dot size) over a wide range, from far infrared to deep ultraviolet. They can be moved around for different purposes:

  • to form quantum-dot "molecules"
  • to form three-dimensional "meta-crystals" that form new materials having tailored lattice constants, tailored crystal symmetry and tailored band structure
  • to act as dopants in other materials
  • to be joined with a larger molecule to form a super molecule.

In this way, instead of 109 elements we have at our disposal, in principle, an unlimited number of atomic "elements."

Figure 1. A single-photon (indicated by a wavy line) coherent (indicated by a double electron line) radiative transition in the presence of an external field (indicated by a dashed virtual photon line), a laser scheme for a three-level atom, and systems of interest (a many-electron atom, a magnetic wiggler for a free-electron laser, and a crystal lattice). Radiation in Matter

Quantum-open-systems (reduced-density-matrix) approaches are developed for non-equilibrium (possibly coherent) electromagnetic interactions in quantized electronic systems, in the presence of environmental relaxation and decoherence phenomena. The electronic systems of interest include ensembles of many-electron atoms, energetic electron beams in crystals and in electric and magnetic fields, and semiconductor materials (ideal crystals and heterostructures). Linear and non-linear optical phenomena are investigated within the frameworks of semi-classical and fully-quantum mechanical (QED) formulations.

Fermi surface of a parent  ferropnictide (LaFeAsO),  colored according to the Fermi velocity Superconductors

Superconducting materials are used in a wide variety of defense and civilian technologies. Navy applications include superconducting motors for electric drives, microwave devices, superconducting magnets, and mine sweeping.

Figure 1. Proposed "double honeycomb chain" structure of Si(111)5x2-Au. Large circles are Au, small circles are Si. The elementary 5x2 unit cell is outlined. Each unit cell contains two honeycomb chains (HC) based on the outlined hexagons, one of alternating Au and Si atoms, the other of all Si. Three additional Si adatoms, with 5x4 periodicity, are also shown. Surfaces and Interfaces

We investigate the physics of clean and adsorbed surfaces of semiconductors and metals. Reduced dimensionality plays an important role at surfaces, profoundly influencing electronic and magnetic properties. We also study the interfaces between materials, which are at the heart of technologically important phenomena such as grain-boundary formation, band-offset engineering, and spin injection.