ampsci

Atomic Many-body Perturbation theory in the Screened Coulomb Interaction

ampsci is a c++ program for high-precision atomic structure calculations of single-valence systems, developed and maintained by Benjamin M. Roberts, University of Queensland, Australia

It solves the correlated Dirac equation using the Hartree-Fock + correlation potential method (based on Dzuba-Flambaum-Sushkov method) to produce a set of atomic wavefunctions and energies. The method is fully relativistic, includes electron correlations, all-orders screening and hole-particle interaction, finite-nuclear size, Breit interaction, radiative QED effects, RPA for matrix elements, and structure radiation/renormalisation. QED is included via the Flambaum-Ginges radiative potential method. Can solve for continuum states with high energy, and calculate ionisation cross sections with large energy/momentum transfer.

Designed to be fast, accurate, and easy to use. The "modules" system (see doc/modules.md) makes it simple to add your own routines to use the atomic wavefunctions to calculate whatever properties you may be interested in.

• The code is on GitHub: github.com/benroberts999/ampsci
• See ampsci.dev/ for full documentation
• A full description of the physics methods and approximations, including references, is given in the physics documentation: ampsci.pdf.
• Important: this is a pre-release version of the code: not fully tested or documented, and should not be used for publishable calculations (without consultation)

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Compilation and usage

Full documentation available online: ampsci.dev/. Divided into sections:

1. Usage intructions, input options
   • Compilation instructions (for linux/mac/windows): doc/compilation.md
   • Detailed info on all input options: doc/ampsci_input.md
   • A basic step-by-step tutorial: doc/tutorial.md
   • A more advanced tutorial: doc/tutorial_advanced.md
     • See also: doc/examples/ampsci.in – an example/template input file
     • In doc/examples/ there are several example input files, with the expected output; use these to test if everything is working
2. Physics documentation: ampsci.dev/ampsci.pdf
   • Description of physics/methods used in the code
   • Includes many references to the works where the methods implemented here were developed.
3. Modules
   • The modules system allows the easy calculation of any atomic properties after the wavefunction has been calculated. See doc/modules.md for description
   • The code is designed so that you can easily create your own modules. See doc/writing_modules.md for details
4. Code documentation – details on classes/functions in the code
   • Available online: ampsci.dev/
   • This should only be required if you plan to edit the code or add new modules

Quick start:

• The setup.sh bash script should install all required dependencies and build ampsci
  • It uses only defaults, and may not work on all systems. See above instructions for full guide to compilation.
• See which ampsci input options are available: ./ampsci -a
  • See available input options for each input block by following with its name
  • e.g., ./ampsci -a HartreeFock
• Check which Modules are aviable: ./ampsci -m
  • See available input options for each module by following with its name
  • e.g., ./ampsci -m MatrixElements
• Check which operators are aviable: ./ampsci -o
  • See available input options for each operator by following with its name
  • e.g., ./ampsci -o hfs

Looking for atomic ionisation form-factors for dark-matter-electron scattering?

• See Kionisation module (./ampsci -m Kionisation)

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