We are pleased to announce the release of version 2020.0 of the MOLSCAT,
BOUND and FIELD programs.
MOLSCAT is a general-purpose package for performing non-reactive quantum
scattering calculations for atomic and molecular collisions using
coupled-channel methods. Simple atom-molecule and molecule-molecule
collision types are coded internally and additional ones may be handled
with plug-in routines. Plug-in routines may include external magnetic,
electric or photon fields (and combinations of them). Simple interaction
potentials may be specified in input data and more complicated ones may
be handled with plug-in routines.
BOUND is a general-purpose package for performing calculations of
bound-state energies of weakly bound atomic and molecular pairs using
coupled-channel methods. It solves the same sets of coupled equations as
MOLSCAT, and can use the same plug-in routines if desired, but applies
bound-state boundary conditions.
FIELD is a development of BOUND that locates values of external fields
at which a bound state exists with a specified energy. One important
use is to locate the positions of magnetically tunable Feshbach
resonance positions in ultracold collisions.
The three programs have different applications, but they use closely
related methods and share many subroutines. They are therefore released
with a single code base and are documented together.
The programs have built-in capabilities to generate the coupled
equations for
- Atom + linear rigid rotor;
- Atom + vibrating diatom;
- Linear rigid rotor + linear rigid rotor;
- Atom + symmetric top;
- Atom + asymmetric top;
- Asymmetric top + linear molecule;
- Atom + rigid corrugated surface: diffractive (elastic) scattering.
For these cases, the programs implement both close-coupling
calculations, with no dynamical approximations, and a variety of
approximate methods including the coupled states and helicity decoupling
approximations. MOLSCAT can loop over total angular momentum (partial
wave) to calculate elastic and inelastic integral cross sections and
spectroscopic line-shape cross sections. It can also locate and
characterise scattering resonances (quasibound states). Post-processors
are available that read MOLSCAT S-matrix files and calculate
differential cross sections, transport, relaxation and
Senftleben-Beenakker cross sections, and fit the parameters of
scattering resonances in more complex cases.
The programs provide an interface for a plug-in basis-set suite to set
up other sets of coupled equations. This capability has been widely used
in bound-state and scattering calculations related to the spectroscopy
of Van der Waals complexes and in ultracold atomic and molecular
collisions. Basis-set suites can be programmed to handle a wide variety
of interacting species and to take account of one or more external
fields, such as electric, magnetic and photon fields. Two examples of
such suites are included in the distribution, for
- closed-shell atom + triplet-Sigma diatom in a magnetic field;
- Alkali-metal atom + alkali-metal atom in a magnetic field, including
hyperfine structure.
For low-energy scattering, MOLSCAT can calculate scattering lengths and
effective ranges and can locate and characterize scattering resonances
as a function of an external variable such as the magnetic field.
New features in version 2020.0 include a capability to converge on and
characterise a scattering resonance or quasibound state as a function of
energy, as described by Frye and Hutson,
https://arxiv.org/abs/1912.00206 . There are also numerous other minor
bug fixes and printing improvements.
Further information on the programs is available at
MOLSCAT: https://doi.org/10.1016/j.cpc.2019.02.014 and
https://arxiv.org/abs/1811.09584
BOUND and FIELD: https://doi.org/10.1016/j.cpc.2019.02.017 and
https://arxiv.org/abs/1811.09111
The full program manual for version 2020.0 (all three programs) is
available at https://arxiv.org/1903.06675. The programs themselves are
free software, distributed under the terms of the GNU General Public
License, Version 3.
The programs are written in FORTRAN 90, though with many features from
older versions of FORTRAN. They have been tested with common FORTRAN
compilers including gfortran and ifort.
The source code may be obtained from https://github.com/molscat/molscat.
No github account is needed. If you are using a Linux machine with git
installed, the commands to create a directory containing the programs are
mkdir molscat
git clone https://github.com/molscat/molscat molscat
On subsequent occasions you can update your source code to the latest
distributed version simply by navigating to the molscat directory and
issuing the command
git pull
Jeremy M. Hutson and C. Ruth Le Sueur
Joint Quantum Centre, Department of Chemistry, University of Durham
--
Prof. Jeremy M. Hutson, FRS
Dept. of Chemistry
University of Durham
Durham
DH1 3LE
England
Tel. 0191 334 2147 (UK)
Tel. +44 191 334 2147 (International)
Web: http://community.dur.ac.uk/j.m.hutson/
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