**An improved version of the Green's function molecular dynamics method**

LT Kong and C Denniston and MH Muser, COMPUTER PHYSICS COMMUNICATIONS, 182, 540-541 (2011).

DOI: 10.1016/j.cpc.2010.10.006

This work presents an improved version of the Green's function molecular
dynamics method (Kong et al., 2009; Campana and Maser, 2004 **1,2**),
which enables one to study the elastic response of a three-dimensional
solid to an external stress field by taking into consideration only
atoms near the surface. In the previous implementation, the effective
elastic coefficients measured at the Gamma-point were altered to reduce
finite size effects: their eigenvalues corresponding to the acoustic
modes were set to zero. This scheme was found to work well for simple
Bravais lattices as long as only atoms within the last layer were
treated as Green's function atoms. However, it failed to function as
expected in all other cases. It turns out that a violation of the
acoustic sum rule for the effective elastic coefficients at Gamma (Kong,
2010 **3**) was responsible for this behavior. In the new version, the
acoustic sum rule is enforced by adopting an iterative procedure, which
is found to be physically more meaningful than the previous one. In
addition, the new algorithm allows one to treat lattices with bases and
the Green's function slab is no longer confined to one layer. New
version program summary Program title: FixGFC/FixGFMD v1.12 Catalogue
identifier: AECW_v1_1 Program summary URL:
http://cpc.cs.qub.ac.uk/summaries/AECW_v1_1.html Program obtainable
from: CPC Program Library, Queen's University, Belfast, N. Ireland
Licensing provisions: Standard CPC licence,
http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed
program, including test data, etc.: 206 436 No. of bytes in distributed
program, including test data, etc.: 4 314 850 Distribution format:
tar.gz Programming language: C++ Computer: All Operating system: Linux
Has the code been vectorized or parallelized?: Yes. Code has been
parallelized using MPI directives. RAM: Depends on the problem
Classification: 7.7 External routines: LAMMPS
(http://lammps.sandia.gov/), MPI
(http://www.mcs.anl.gov/research/projects/mpi/), FFT
(http://www.fftw.org/) Catalogue identifier of previous version:
AECW_v1_0 Journal reference of previous version: Comput. Phys. Comm. 180
(2009) 1004 Does the new version supersede the previous version?: Yes
Nature of problem: Green's function molecular dynamics (GFMD) is a
coarse-graining method that enables one to investigate the full elastic
response of an interface between a semi-infinite solid and a contact
while taking only the surface atoms in the solid into consideration. The
effect of long-range elastic deformations on the surface atoms from the
semi-infinite solid is replaced by effective elastic interactions, thus
reducing the problem from three dimensions to two dimensions without
compromising the physical essence of the problem.

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