Extensible periodic table of the elements

Release 1.3, Dec 7, 2010

This package provides a periodic table of the elements with support for mass, density and xray/neutron scattering information.

Masses, densities and natural abundances come from the NIST Physics Laboratory, but do not represent a critical evaluation by NIST scientists.

Neutron scattering calculations use values collected by the Atomic Institute of the Austrian Universities. These values do corresponding to those from other packages, though there are some differences depending to the tables used. Bound coherent neutron scattering for gold in particular is significantly different from older value: 7.63(6) as measured in 1974 compared to 7.90(7) as measured in 1990.

X-ray scattering calculations use a combination of empirical and theoretical values from the LBL Center for X-ray Optics. These values differ from those given in other sources such as the International Tables for Crystallography, Volume C, and so may give different results from other packages.

Change history

1.3 2010-12-05

New:

• mix_by_weight and mix_by_volume formula constructors
• use natural density to set density for isotope specific formulas
• add neutron_scattering function which returns xs, sld and penetration depth

Modified:

• need wavelength= or energy= for xray/neutron sld
• improved docs and testing

1.2 2010-04-28

New:

• support pickle: id(H) == id(loads(dumps(H)))
• support ions, with magnetic form factors and x-ray f0 scattering factor
• support py2exe wrappers
• allow density to be calculated from structure (bcc, fcc, hcp, cubic, diamond)
• estimate molecular volume
• support private tables with some values replaced by application

Modified:

• rename package periodictable
• rename table to periodictable.elements
• neutron sld returns real and imaginary coherent and incoherent instead of coherent, absorption and incoherent
• bug fix: sld for H[2] was wrong when queried before sld for H.
• remove CrysFML ionic radius definitions

1.1 2009-01-20

Modified:

• Restructure package, separating tests into different directory

• When defining table extensions, you should now do:

  from elements.core import periodic_table, Element, Isotope
  

  rather than:

  from elements import periodic_table
  from elements.elements import Element, Isotope