ECs
===

Andy Nowacki
a.nowacki@leeds.ac.uk

ECs contains elastic constants for materials present in the Earth, taken from
various publications and transcribed to machine-readable format.


Useful tools
------------
These elastic constants can be easily manipulated using my Elasticity programs,
which you can check out using git at:
	https://github.com/anowacki/elasticity.git
They rely on my Fortran codes for dealing with geophysics problems, which are
at:
	https://github.com/anowacki/seismo-fortran.git

You can check them out using git like this:
	$ git clone https://github.com/anowacki/elasticity.git


File format
-----------
Files are in the .ecs format as read by, for instance, my Fortran 
(https://github.com/anowacki/seismo-fortran.git), and
MSAT (http://www1.gly.bris.ac.uk/MSAT/).  These are in the following format:
	i j Cij
where i and j are the Voigt matrix elastic tensor representation column and row
number, and Cij is the corresponding elastic constant in Pa.

When i=j=7, the value is the density, in kg/m^3.

Comments may be made in the files when the first character on the line is a '%'
or '#' character.  Comments may also be placed after the Cij value (at least
with my 'anisotropy_ajn' module and codes).

Most files are named according to the following convention:
	[formula]_[phase]_[pressure]GPa_[temperature]T_[author]_[journal]_[year].ecs
Some files, however, have terser or incomprehensible names.  Equally, previous
codes could not cope with reading files with comments, so older .ecs files will
not have all details in the file as newer ones will.


Executable files
----------------
As a primitive way of coping with cases where the elastic constants and density
can be expressed as a continuous function with pressure and/or temperature
(i.e., when the derivatives are available), executable shell scripts will
produce the constants given a P and/or T.  These are named:
	[formula]_[phase]_xP_xT_[author]_[journal]_[year].ecs

Other shell scripts are present to automatically produce the .ecs files from the
raw data supplied with publications, or transcriptions of tables in the printed
versions.


Creating .ecs files
-------------------
Probably the best way of entering a one-off set of elastic constants is using
the 'enter-ecs' script, available as part of my elasticity tools. The script
will ask for the symmetry of the constants and only ask for the unique values
needed.  If you don't know the density, but do know the unit cell volume and
the atoms in the unit cell, it will calculate density for you as well.  You can
then enter as many comment lines as you like to describe the publication,
experimental details, etc., and the formatting will be ensured to be correct.


Plotting .ecs files
-------------------
If you have installed my tools, then you can just do
	$ CIJ_plot file.ecs
to see a phase velocity surface for Vp and AVs.  Type 'CIJ_plot -h' to see the
help.