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—Staggering computational and algorithmic advances in recent years now make possible systematic Quantum Monte Carlo (QMC) simulations of high temperature (high-Tc) su-perconductivity in a microscopic model, the two dimensional (2D) Hubbard model, with parameters relevant to the cuprate materials. Here we report the algorithmic and computational advances(More)
Further developments are introduced in the theory of nite size errors in quantum many{body simulations of extended systems using periodic boundary conditions. We show that our recently introduced Model Periodic Coulomb interaction A. J. Williamson et al., Phys. Rev. B 55, R4851 (1997)] can be applied consistently to all Coulomb interactions in the system.(More)
The energetic stability of structural isomers of C 24 , C 26 , C 28 , and C 32 clusters, including fullerenes, is studied using diffusion quantum Monte Carlo methods. We predict that a C 24 isomer is the smallest stable graphitic fragment and that the smallest stable fullerenes are the C 26 and C 28 clusters with C 2v and T d symmetry, respectively. Given(More)
Quantum Monte Carlo ͑QMC͒ techniques are used to calculate the one-body density matrix and excitation energies for the valence electrons of bulk silicon. The one-body density matrix and energies are obtained from a Slater-Jastrow wave function with a determinant of local-density approximation ͑LDA͒ orbitals. The QMC density matrix evaluated in a basis of(More)
Perfect crystals are rare in nature. Real materials often contain crystal defects and chemical order/disorder such as grain boundaries, dislocations, interfaces, surface reconstructions and point defects. Such disruption in periodicity strongly affects material properties and functionality. Despite rapid development of quantitative material characterization(More)
The emergence of two-dimensional metallic states at the LaAlO3/SrTiO3 (LAO/STO) heterostructure interface is known to occur at a critical thickness of four LAO layers. This insulator to-metal transition can be explained through the "polar catastrophe" mechanism arising from the divergence of the electrostatic potential at the LAO surface. Here, we(More)
QMCPACK is open source scientific software designed to perform Quantum Monte Carlo (QMC) simulation, a first-principles method for describing many-body systems. The evaluation of each Monte Carlo move requires finding the determinant of a dense matrix in the wave functions. This calculation forms a key computational kernel in QMCPACK. After each accepted(More)
The recently synthesized freestanding four-atom-thick double-layer sheet of ZnSe holds great promise as an ultraflexible and transparent photoelectrode material for solar water splitting. In this work, we report theoretical studies on a novel three-atom-thick single-layer sheet of ZnSe that demonstrates a strong quantum confinement effect by exhibiting a(More)
Computational Earth Sciences Group members Tianyu Jiang and Kate Evans published the paper " Intermediate Frequency Atmospheric Disturbances: A Dynamical Bridge Connecting western U.S. Extreme Precipitation with East Asian Cold Surges in linking atmospheric weather extremes " in J. Geophysical Research: Atmospheres with collaborators at Georgia Tech and the(More)
Crystalline micrometer-long YSi2 nanowires with cross sections as small as 1 × 0.5 nm(2) can be grown on the Si(001) surface. Their extreme aspect ratios make electron conduction within these nanowires almost ideally one-dimensional, while their compatibility with the silicon platform suggests application as metallic interconnect in Si-based nanoelectronic(More)