School of Civil and Environmental Engineering

Ph.D. Thesis Defense Announcement

Efficient Large-Scale Real-Space Electronic Structure Calculations

By

Swarnava Ghosh

Advisor:

Dr. Phanish Suryanarayana (CEE)

Committee Members:

Dr. Glaucio H. Paulino (CEE), Dr. Arash Yavari (CEE),

Dr. Ting Zhu (ME), Dr. John E. Pask (Lawrence Livermore National Laboratory)

Date & Time: Thursday, July 7, 2016, at 10:30AM

Location: Sustainable Education Building, 122

Calculations involving the electronic structure of matter provides valuable insight in understanding and predicting a wide range of materials

properties. Over the course of the last few decades, Density Functional Theory (DFT) has been a reliable and popular ab-initio method. The

plane-wave basis is commonly employed for solving the DFT problem. However, the need for periodicity limits the effectiveness of the

plane-wave basis in studying localized or partially periodic systems. Furthermore, efficient use utilization modern large-scale computer

architectures is particularly challenging due to the non-locality of the basis. Real-space methods for solving the DFT problem provide an

attractive alternative.

In this work we present an accurate and efficient real-space formulation and parallel implementation of Density Functional Theory (DFT) for

performing ab-initio simulations of isolated clusters (molecules and nanostructures), periodic (infinite crystals) and partially periodic systems

(slabs and nanowires). Using the finite-difference representation, local reformulation of the electrostatics, the Chebyshev polynomial filtered

self-consistent field iteration, and a reformulation of the non-local component of the force, we develop SPARC (Simulation Package for

Ab-initio Real-space Calculations), a framework that enables the efficient evaluation of energies and atomic forces to within chemical

accuracies in DFT. Through selected examples consisting of a variety of elements, we demonstrate that the developed framework obtains

exponential convergence in energy and forces with domain size; systematic convergence in the energy and forces with mesh-size to reference

plane-wave result at comparably high rates; forces that are consistent with the energy, both free from any noticeable `egg-box' effect; and

accurate ground-state properties including equilibrium geometries and vibrational spectra. We also demonstrate the weak and strong scaling

behavior of SPARC and compare with well-established and optimized plane-wave and other real-space implementations of DFT for systems

consisting up to thousands of electrons. Overall, the developed framework is able to accurately and efficiently simulate the electronic

structure of a wide range of material systems and represents an attractive alternative to existing codes for practical DFT simulations.