Fast Parallel Total Energy Methods for Multiple Length Scales

Project CCM6 of the

Common High Performance Computing Software Support Initiative (CHSSI)

The Fast Parallel Total Energy Methods for Multiple Length Scales project is designed to

• Develop a scalable software suite for calculating total energies and forces on atoms in systems ranging from 10-100 atoms to systems containing millions of atoms.
  
  
• Produce easily maintainable scalable code, using Fortran 77, Fortran 90, and MPI, which will run on DoD parallel computers, in particular at the Major Shared Resource Centers (MSRC) and Distributed Centers (DC) of the Department of Defense High Performance Computing Modernization Program.
  
  
• Provide manuals and training for DoD researchers who wish to use these codes.

The project is divided into three modules. Each module has its own web page, which may be reached by clicking on the title:

Tight-Binding Total Energy (TB)

Hundreds of atoms

The Tight-Binding module is a continuation of CHSSI project CCM3, DoD-Parallel Tight-Binding Molecular Dynamics. The new project includes

• Tight-binding with self-consistent charge transfer
  
  
• Development of a library of binary alloy parameters for studying the behavior of two-component systems. Ternary parameters will also be developed.

Self-Consistent Atomic Deformation (SCAD)

Hundreds of atoms

The Self-Consistent Atomic Deformation (SCAD) method is a first-principles based alternative to the standard Kohn-Sham ansatz for Density Functional Theory. The the computational effort involved in the SCAD method scales linearly with the number of atoms in the system, a property known as ``order-N'' (O[N]) behavior. The method is also easily parallelized. The SCAD method is particularly well-suited for the study of ionic and semi-conducting systems.

CCM-6 makes the scalable SCAD code available. This allows the user to compute total energy as a function of atomic positions for arbitrary crystal structures.

Atomistic Potentials (AP)

Thousands of atoms

This module is in two parts:

• A library of atomistic potentials, based on the Embedded atom method, designed to reproduce the results of first-principles calculations over a wide range of structures, and
  
  
• The scalable Simulator of Lattice Defects (SOLD) code, which allows the user to perform molecular dynamics simulations on large-scale structures, including isolated vacancies, interstitial substitutions, anti-site defects, dislocations, grain boundaries, and cracks. The SOLD code can handle many more atoms than the TB or SCAD codes, but may be inaccurate in extreme situations. In these regimes results should be checked with the SCAD or TB methods, or with another first-principles code.
  
  

The Operational Test Readiness Review (OTRR) for CCM-6 on 11 February 2003. The tests performed for this review, including a discussion of all Critical Technical Parameters, were summarized in a document prepared for the external reviewers. Following the OTRR this document was revised. The Revised CCM6 Report to the External Reviewers presents useful information about the performance of the CCM-6 modules. It will be referred to in the Lessons Learned section of each modules web page.

All of our codes require registration, which can be accomplished by going to our CHSSI CCM-3 and CCM-6 Code Registration page, filling out the form, and waiting for your passwords.