Elastic: A tool for calculating second-order elastic constants from first principles and for any crystal structure.

by **Algerien1970** Fri 22 May - 1:43

Elastic: A tool for calculating second-order elastic constants from first principles and for any crystal structure.

To download the package clik on the link below :

http://exciting.wdfiles.com/local--files/elastic/ElaStic_1.0.tar.gz

Elastic: A tool for calculating second-order elastic constants from first principles and for any crystal structure. 10422522_10206543030917024_30237666192216826_n

by **Algerien1970** Sat 30 May - 16:58

ReadMe file :

ABOUT
=======

<< Welcome to ElaStic_1.0 >>

This software package allows you to obtain full second-order elastic tensors (elastic constants)
for all crystal lattice types and third-order elastic constants for cubic, hexagonal, and
rhombohedral crystals.
This code is written in Python programming language and uses the SGROUP tool as symmetry and
space-group calculator and utilizes Exciting, Wien2k and Quantum Espresso density-functional codes
for energy and stress calculations.

DESCRIPTION
=============

In order to use "ElaStic" software package, please follow the steps below:
STEP 0.1:
The "ElaSticROOT" shell variable must be set by the user. For instance, add the following
line with the correct "ElaStic" path, in the ".bashrc" file:
export ElaSticROOT=/home/dir1/dir2/ElaStic

STEP 0.2:
Download and install "SGROUP" program:
This program is a utility which allows "ElaStic" to determine the space-group and symmetry
operations of a crystal structure. More information can be found in:

Programmers : B.Z. Yanchitsky, A.N. Timoshevskii
Download Link : http://cpc.cs.qub.ac.uk/summaries/adon
Journal Reference : Comput. Phys. Commun. 139(2001)235

You can also find "SGROUP" program in the file "adon_v1_0.tar.gz" in "ElaStic"
directory: Go to the "ElaStic" directory or where you saved this zipped file and execute the
following commands ($ means command line in a terminal):

$ tar xfvp adon_v1_0.tar.gz
$ cd SpaceGroups
$ make
$ cp sgroup $ElaSticROOT

You can find more information about "SGROUP" program in "SpaceGroups/README" file.

STEP 1.1:
In order to generate input files for a series of distorted structure, run the following script
from the command line:

$ ElaStic_Setup

This program requires a structural input file which can be the same as the input file of the
following DFT codes:

exciting (http://exciting-code.org/)
WIEN2k (http://www.wien2k.at/)
Quantum ESPRESSO (http://www.quantum-espresso.org/)

Once the input file is ready, "ElaStic" requires these values:

-The order of the elastic constants which you are interested in calculating.
-The absolute value of the maximum strain.
-Number of deformed structures equally spaced between the maximum negative strain and the
maximum positive one.

Entries must be typed on the screen when they are requested.

STEP 1.2:
Calculate the energy or stress tensor of deformed structure using one of the mentioned DFT
codes.

NOTICE to "WIEN2k" users:
A shell script program is provided under the name "ElaStic_WIEN2k_init" which allows you
to initialize the deformed structures automatically.
Before executing this program, you must specify input variables of "WIEN2k" calculations.
It is recommended to copy this file to the directory where "Dst??" directories, e.g. Dst01,
exist. Then, modify line 23 of this program according to the accuracy of your calculations.

The "WIEN2k_init_lapw_silent" script is the modified script file of the "init_lapw" program.
You find FLAGS of "WIEN2k_init_lapw_silent" program if you write following command in terminal:

$ WIEN2k_init_lapw_silent -H

Once the WIEN2k calculations are finished, you can run the following scripts to save and clean
your calculations.

$ ElaStic_Save_Clean_WIEN2k

NOTICE to "Quantum ESPRESSO" users:
The output file must be saved under same name of the input file but with ".out" extension.
For instance, if a given input file is named as "Dst02_25.in", the output file must be saved
as "Dst02_25.out".

STEP 2.1:
In order to calculate elastic constants accurately, you have to analyze your calculations,
first.
The script "ElaStic_Analyze" allows you to analyze the dependence of the calculated
derivatives of the "energy-vs-strain" or "energy-vs-stress" curves on the two following
parameters:

-The range of distortions.
-The degree of the polynomial fit.

The script can be run giving the following command in terminal:

$ ElaStic_Analyze

At this point, "xmgrace" plots automatically appear on your screen. For each distortion,
you can find the best distortion range and the best order of polynomial fit. You can find more
details about these issues in "ElaStic_Paper.pdf".

STEP 2.2:
In order to obtain the numerical values of the second- and third-order elastic constants,
you should edit the "ElaStic_2nd.in" and "ElaStic_3rd.in", respectively.

In each row of these files, you should insert a value for "eta_max" and "Fit_order". According
to the result of the visual analysis of the figures in the previous step, these two values are
extracted by considering the plateau regions of the corresponding plot: "eta_max" is a value
of maximum distortion located in the plateau region of the curve representing the polynomial
fit of order "Fit_order".

STEP 3.0:
At this stage, in order to calculate elastic constants and moduli, run the following script:

$ ElaStic_Result

Numerical values of the elastic constants are output in "ElaStic_2nd.out" and
"ElaStic_3rd.out" files for the second- and third-order elastic constants, respectively.

POST-PROCESSING PROGRAMS
==========================

1- "ElaStic_xyz2XYZ" is a program to transform elastic constants from one Cartesian coordinate
to another Cartesian systems.
In order to transform elastic constant tensor from an old Cartesian coordinate system to a new
one, "ElaStic" requires two input files:

i - The output file of "ElaStic" (ElaStic_2nd.out).
ii- A file with "Transformation_Matrix" name. This file contains 3X3 matrix in following
format:
i'.i i'.j i'.k
j'.i j'.j j'.k
k'.i k'.j k'.k
where i', j' and k' are the unit vectors in the new system and i, j and k are the
unit vectors in old Cartesian coordinate systems. Dot (.) indicates the "dot product" of two
vectors.

2- "ElaStic_Analyze_B0" is a program to check the dependence of the bulk modulus (B0) and its
pressure-derivative (B0') on the range of distortion and the degree of the polynomial fit
parameters.
This program requires an input file, with an arbitrary name, which contains volume and energy
value in two columns.

REFRANCE PAPER
================

ElaStic: A tool for calculating second-order elastic constants from first principles
Computer Physics Communications 184, 1861-1873 (2013).
This article contains method, the numerical algorithm and results which are calculated with ElaStic.
In case of publication, if you used ElaStic for any purpose, please cite this reference.

CONTACT
=========

If you have any suggestion or you found any bug, please write to

E-mail: rostam@physik.hu-berlin.de

Rostam Golesorkhtabar
Humboldt-UniversitÃ¤t zu Berlin
Institut fÃ¼r Physik und IRIS Adlershof, Theoretische FestkÃ¶rperphysik

Zum Grossen Windkanal 6, 12489 Berlin, Germany.

Elastic: A tool for calculating second-order elastic constants from first principles and for any crystal structure.

Elastic: A tool for calculating second-order elastic constants from first principles and for any crystal structure.

Re: Elastic: A tool for calculating second-order elastic constants from first principles and for any crystal structure.