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This article describes the variational and fixed-node diffusion quantum Monte Carlo methods and how they may be used to calculate the properties of many-electron systems. These stochastic wave-function-based approaches provide a very direct treatment of quantum many-body effects and serve as benchmarks against which other techniques may be compared. They(More)
The concept of GRASS (Geographic Resources Analysis Support System) as an open system has created a favorable environment for integration of process based modeling and GIS. To support this integration a new generation of tools is being developed in the following areas: a) interpolation from multidimensional scattered point data, b) analysis of surfaces and(More)
Spatial and spatio-temporal distributions of both physical and socioeconomic phenomena can be approximated by functions depending on location in a multi-dimensional space, as multivariate scalar, vector, or tensor fields. Typical examples are elevations, climatic phenomena, soil properties, population densities, fluxes of matter, etc. While most of these(More)
Application of spline approximation method to computation and analysis of lidar-based digital elevation models is investigated to determine its accuracy and capability to create surfaces at different levels of detail. Quadtree segmentation that adapts to the spatial heterogeneity of data points makes the method feasible for large data sets. The results(More)
*Helena Mitasova, Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, 1120 Jordan Hall, Raleigh, NC, USA; Lubos Mitas, Department of Physics, North Carolina State University, Raleigh, NC, USA; William M. Brown, Geographic Modeling Systems Laboratory, Department of Geography, 220 Davenport Hall, University of Illinois at(More)
We investigate the accuracy of trial wave functions for quantum Monte Carlo based on Pfaffian functional form with singlet and triplet pairing. Using a set of first row atoms and molecules we find that these wave functions provide very consistent and systematic behavior in recovering the correlation energies on the level of 95%. In order to get beyond this(More)
Regularized Spline with Tension (RST) is an accurate, flexible and efficient method for multivariate interpolation of scattered data. This study evaluates its capabilities to interpolate daily and annual mean precipitation in regions with complex terrain. Tension, smoothing and anisotropy parameters are optimized using the crossvalidation technique. In(More)
Emerging technologies that combine the flexibility of digital landscape representation with easy-to-interpret 3D physical models open new possibilities for user interaction with geospatial data. A prototype tangible geospatial modeling environment lets users interact with landscape analysis and simulations using a tangible physical model. We introduce a(More)
We investigate pfaffian trial wavefunctions with singlet and triplet pair orbitals by quantum Monte Carlo methods. We present mathematical identities and the key algebraic properties necessary for efficient evaluation of pfaffians. Following upon our previous study Bajdich et al., Phys. Rev. Lett. 96, 130201 2006 , we explore the possibilities of expanding(More)