TOPS Opacities

Opacities of mixtures (calculated by TOPS using ATOMIC or LEDCOP elemental opacities)




The material data were last updated on August 19, 2015. This latest update includes OPLIB tables generated with the ATOMIC code, which (compared to the earlier LEDCOP release) cover additional temperatures and extend to higher densities.

Users are encouraged to view the File of currently available materials page to learn about the new data options.


Link to: Los Alamos Astrophysical Opacity Page

Precalculated Rosseland opacity tables for complex astrophysical mixtures are now available.


Fill in form, then submit. Multiple values (where appropriate) must be separated by spaces. Leave field empty for default value. As a help to new users, the initial Web page defaults to calculating gray mean opacities for aluminum.

Relevant information:


Source of elemental opacities

ATOMIC LEDCOP Most recent available


Mix specification

Fraction by Number or Mass.
Input format is Fraction, Element or Fraction, Element, Isotopic weight.

In specifying a mix, the fraction represents relative numbers of atoms if the number fraction box is checked. If the mass fraction box is checked, the fraction represents relative masses of the specified elements. The fractions need not be normalized.

The element specification can be the atomic number, the chemical symbol (case insensitive) or the OPLIB matid. Thus aluminum can be specified as Al, al, 13, or n13719.

If the "Fraction, Element, Isotope" box is checked, a specific isotopic weight must be entered for each element of the mixture. If this box is not checked, no isotopic weight should be entered, the Web Page will use the normal values.

User specified mixture. Up to 450 characters may be used for the mixture specification. User can choose to supply a name for the mixture, up to 15 characters.


Optional Mixture Name: (User supplied, maximum of 15 characters)


Temperatures (in keV)

Specific temperatures--must be in data base, see range values below or Temperature list

Temperature range:Minimum: Maximum:
Thin database table with stride of (The resulting grid always starts with the lowest temperature.)


Densities (in g/cm3)

Specific densities:

values (max  100) in range to with spacing
Read Standard SESAME densities) to get normal SESAME library density grid.


Photon energy group bounds (in keV)

Specific photon energies (at least 2 if this option is chosen):

values (max 1000) in range to with spacing
Photon energy grid need not be specified for gray mean opacities or frequency dependent opacities.


Output Data Type options (Gray mean opacities by default)

Gray mean opacities only

If users wish to examine the opacities in more detail, choose one of the options below (you still get the Gray mean opacities), but users should restrict the number of temperature-density-multigroup energy points to maintain a reasonable size data base for plotting and transmitting the data.

Multigroup opacities

No more than 6 temperature-density points for the last 2 options.

Frequency dependent opacities (Not Spectroscopically Resolved)
Both multigroup and frequency dependent opacities


Useful Links

Group T-1 home page.......... Astro Opacity Web Page.


Please mail questions or comments to:
LANL T-1 Opacities <opacity@lanl.gov>

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Los Alamos Report No. LA-UR-01-1257

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Last Modified: <Oct. 29, 2012>

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