Condensed Matter Theory

The research activities of the Condensed Matter Theory (CMT) group (Dr. C.S. Jayanthi,Dr. S. Liu, Dr. M. Yu) focus on the structural, electronic, and transport properties of low- dimensional material systems using the state-of-the-art computer simulation techniques. Our research interests focus around developing methodologies for efficient large-scale simulations, exploring the properties of low-dimensional materials for potential technological applications, and obtaining a fundamental understanding of the roles played by dimensionality, shape, and size in altering the material properties.

Our computational studies use both ab-initio and quantum mechanics based simulations. Some of the notable methodological developments of the CMT group include: (i) a linear scaling algorithm for large-scale electronic structure calculations and molecular dynamics simulations, (ii) a quantum electronic transport code, and (iii) a state-of-the-art semi-empirical Hamiltonian (SCED-LCAO), developed in the framework of a linear combination of atomic orbitals (LCAO), for large-scale quantum mechanics based simulations.

The salient feature of this LCAO based semi-empirical method is that it models electron screening in a multi-atom environment through suitably designed parameterized functions with its framework allowing for charge self-consistency. Using the SCED-LCAO molecular dynamics, we have investigated the optimized structures of a wide-variety of condensed matter systems (bulk and reduced symmetry phases), materials (covalently bonded, three-centered two-electron materials, etc.), different morphologies, etc. that demonstrate the robustness and predictive power of this method.

Some selected recent studies based on the SCED-LCAO method include theoretical predictions of stable structures of two-dimensional boron sheets based on B12 icosahedral structures, tuning the energy gap of carbon flakes embedded in hexagonal boron nitride sheets, etc.

Other studies using the SCED-LCAO method include:

• The initial stage of growth of single-wall carbon nanotubes
• The energetics and size-dependent properties of different families of carbon clusters
• The adsorption energy mapping of silicon adsorbed on Si(111)-7x7
• Theoretical predictions of bucky diamond silicon carbide and SiC cage structures
• The relative stability studies of different morphologies of silicon nanowires, silicon carbide nanowires, etc.

Selected Publications on SCED-LCAO

1. Next Generation of the Self-Consistent and Environment-Dependent Hamiltonian: Applications to Various Boron Allotropes from Zero- to Three-Dimensional Structures, P. Tandy, M. Yu, C. Leahy, C.S. Jayanthi, and S.Y. Wu, J. Chem. Phys. 142, 124106 (2015).
2. Low-dimensional boron structures based on icosahedrons B12, C. B. Kah, M. Yu, P. Tandy, C. S. Jayanthi, and S. Y. Wu, Nanotechnology 26, 405701 (2015).
3. Initial stage of growth of single-walled carbon nanotubes: modelling and simulations, I. Chaudhuri , Ming Yu, C. S. Jayanthi, and S. Y. Wu, J. Phys. Condensed Matter 26, 115301 (2014)
4. Size, Shape, and Orientation-Dependent Properties of SiC Nanowires of Selected Bulk Polytypes”, Ming Yu, C. S. Jayanthi, and S. Y. Wu, J. Material Research Focus Issue, 28, 57 (2013)
5. Theoretical Perditions of SiC bucky-diamond Cluster, Ming Yu, C. S. Jayanthi, and S. Y. Wu, Nanotechnology 23, 235705 (2012).
6. A self-Consistent and Environment-Dependent Hamiltonian for large Scale Simulations of Complex Nanostructures, Ming Yu, S.Y. Wu, and C.S. Jayanthi, Physica E 42, 1 (2009).

• Dr. Chakram S. Jayanthi google scholar
• Dr. Ming Yu's google scholar

Research Assistant Professor

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Undergraduate Students

• Development of an order-N scheme for large scale simulations
• Development of a Local Analysis tool
• Development of Real Space Techniques to study vibrational and electronic properties of systems with low symmetry.
• Surface Structure and Dynamics.
• Surface Phase Transitions
• Lattice Dynamics of Fractals, Incommensurate Structures, and Alloys.
• Electronic Structure Calculation of Semiconducting Clusters and Surfaces via Real Space Tight-Binding LMTO method.

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