20 research outputs found
Scalable computational approach to extract chemical bonding from real-space density functional theory calculations using finite-element basis: A projected orbital and Hamiltonian population analysis
We present an efficient and scalable computational approach for conducting
projected population analysis from real-space finite-element (FE) based
Kohn-Sham density functional theory calculations (DFT-FE). This work provides
an important direction towards extracting chemical bonding information from
large-scale DFT calculations on materials systems involving thousands of atoms
while accommodating periodic, semi-periodic or fully non-periodic boundary
conditions. Towards this, we derive the relevant mathematical expressions and
develop efficient numerical implementation procedures that are scalable on
multi-node CPU architectures to compute the projected overlap and Hamilton
populations. This is accomplished by projecting either the self-consistently
converged FE discretized Kohn-Sham eigenstates, or the FE discretized
Hamiltonian onto a subspace spanned by localized atom-centered basis set. The
proposed method is implemented in a unified framework within DFT-FE where the
ground-state DFT calculations and the population analysis are performed on the
same finite-element grid. We further benchmark the accuracy and performance of
this approach on representative material systems involving periodic and
non-periodic DFT calculations with LOBSTER, a widely used projected population
analysis code. Finally, we discuss a case study demonstrating the advantages of
our scalable approach to extract the chemical bonding information from
increasingly large silicon nanoparticles up to a few thousand atoms.Comment: 9 Figures, 5 Tables, 53 pages with references and supplementary
informatio
Roadmap on Electronic Structure Codes in the Exascale Era
Electronic structure calculations have been instrumental in providing many important insights into a range of physical and chemical properties of various molecular and solid-state systems. Their importance to various fields, including materials science, chemical sciences, computational chemistry and device physics, is underscored by the large fraction of available public supercomputing resources devoted to these calculations. As we enter the exascale era, exciting new opportunities to increase simulation numbers, sizes, and accuracies present themselves. In order to realize these promises, the community of electronic structure software developers will however first have to tackle a number of challenges pertaining to the efficient use of new architectures that will rely heavily on massive parallelism and hardware accelerators. This roadmap provides a broad overview of the state-of-the-art in electronic structure calculations and of the various new directions being pursued by the community. It covers 14 electronic structure codes, presenting their current status, their development priorities over the next five years, and their plans towards tackling the challenges and leveraging the opportunities presented by the advent of exascale computing
Roadmap on electronic structure codes in the exascale era
Electronic structure calculations have been instrumental in providing many important insights into a range of physical and chemical properties of various molecular and solid-state systems. Their importance to various fields, including materials science, chemical sciences, computational chemistry, and device physics, is underscored by the large fraction of available public supercomputing resources devoted to these calculations. As we enter the exascale era, exciting new opportunities to increase simulation numbers, sizes, and accuracies present themselves. In order to realize these promises, the community of electronic structure software developers will however first have to tackle a number of challenges pertaining to the efficient use of new architectures that will rely heavily on massive parallelism and hardware accelerators. This roadmap provides a broad overview of the state-of-the-art in electronic structure calculations and of the various new directions being pursued by the community. It covers 14 electronic structure codes, presenting their current status, their development priorities over the next five years, and their plans towards tackling the challenges and leveraging the opportunities presented by the advent of exascale computing
Roadmap on Electronic Structure Codes in the Exascale Era
Electronic structure calculations have been instrumental in providing many important insights into a range of physical and chemical properties of various molecular and solid-state systems. Their importance to various fields, including materials science, chemical sciences, computational chemistry and device physics, is underscored by the large fraction of available public supercomputing resources devoted to these calculations. As we enter the exascale era, exciting new opportunities to increase simulation numbers, sizes, and accuracies present themselves. In order to realize these promises, the community of electronic structure software developers will however first have to tackle a number of challenges pertaining to the efficient use of new architectures that will rely heavily on massive parallelism and hardware accelerators. This roadmap provides a broad overview of the state-of-the-art in electronic structure calculations and of the various new directions being pursued by the community. It covers 14 electronic structure codes, presenting their current status, their development priorities over the next five years, and their plans towards tackling the challenges and leveraging the opportunities presented by the advent of exascale computing
DFT-FE – A massively parallel adaptive finite-element code for large-scale density functional theory calculations
We present an accurate, efficient and massively parallel finite-element code, DFT-FE, for large-scale ab-initio calculations (reaching ~100,000 electrons) using Kohn–Sham density functional theory (DFT). DFT-FE is based on a local real-space variational formulation of the Kohn–Sham DFT energy functional that is discretized using a higher-order adaptive spectral finite-element (FE) basis, and treats pseudopotential and all-electron calculations in the same framework, while accommodating non-periodic, semi-periodic and periodic boundary conditions. We discuss the main aspects of the code, which include, the various strategies of adaptive FE basis generation, and the different approaches employed in the numerical implementation of the solution of the discrete Kohn–Sham problem that are focused on significantly reducing the floating point operations, communication costs and latency. We demonstrate the accuracy of DFT-FE by comparing the energies, ionic forces and periodic cell stresses on a wide range of problems with popularly used DFT codes. Further, we demonstrate that DFT-FE significantly outperforms widely used plane-wave codes—both in CPU-times and wall-times, and on both non-periodic and periodic systems—at systems sizes beyond a few thousand electrons, with over 5-10 fold speedups in systems with more than 10,000 electrons. The benchmark studies also highlight the excellent parallel scalability of DFT-FE, with strong scaling demonstrated on up to 192,000 MPI tasks
Vibration behavior of thin-walled steel members subjected to uniform bending
This article reports the results of an investigation on the effects of internal moments
on the vibration behavior of thin-walled steel members. The analyses are based
on the Generalized Beam Theory (GBT), a thin-walled bar theory accounting for crosssection
in-plane deformations ? its main distinctive feature is the representation of the
member deformed configuration by means of a linear combination of cross-section
deformation modes, multiplied by their longitudinal amplitude functions. The study
concerns a simply supported T-section (with unequal flanges) members exhibiting a
wide range of lengths and subjected to uniform internal moment diagrams ? their magnitudes
are specified as percentages of the corresponding critical buckling values. After
providing a brief overview of the main concepts and procedures involved in performing
a GBT-based structural analysis, the vibration behavior of load-free and loaded T-section
members is addressed ? the influence of the applied loadings is assessed in terms of
(i) the fundamental frequency difference and (ii) the change in the corresponding vibration
mode shape. For validation purposes, some GBT results are compared with values
yielded by shell finite element analysis performed in the code ABAQUS (Simulia, 2008)