Shared Components

Nautilus provides a set of shared components, essentially pieces that were originally written for Singe but were identified as being potentially useful to SuNRe. These components provide a place to share code instead of reimplementing features, but they may be superseded as newer tools are developed within Nautilus.

Nautilus makes use of common terms and symbols for atomic nuclei, which are summarized here.

Be aware that the components described on this page were developed before certain terminology was clarified, and so it may not match the terminology as used in the discussion of the EntityTag class, which was designed to address the confusion of terminology and standards more carefully.

SZA

An SZA is a way to denote a particular nuclide. Due to its use in various data libraries, such as the Nuclear Data Interface (NDI), the SZA is common in many codes.

Depending on your specific use-cases, you may want to consider the newer EntityTag instead of an SZA, as it addresses some corner cases and better supports conversions between different formats. However, the SZA class is still supported as the more minimal design may be more appropriate for some applications.

An SZA is an integer value, defined as

\[\text{SZA} = S * 1{,}000{,}000 + Z * 1{,}000 + A\]

Nautilus provides the SZA class, which stores the SZA value and provides the following accessors:

  • A() – the atomic mass number

  • N() – the neutron number

  • S() – the metastable index

  • Z() – the atomic number

It also provides the following additional operations:

  • explicit cast to an integer value

  • all comparison operators: <, <=, ==, !=, >=, >; comparison is ordered first by \(Z\), then by \(A\) for nuclides with the same \(Z\) value, then by \(S\) for nuclides with the same \(Z\) and \(A\) values

Nuclide

The Nuclide class is based on the Isotope class from Singe. For compatibility there is an alias called Isotope in Nautilus, but it is deprecated.

The Nuclide class consists of an SZA and a mass, providing a slightly more detailed description of the nuclide in question. It provides the following accessors:

  • A() – the atomic mass number

  • N() – the neutron number

  • S() – the metastable index

  • Z() – the atomic number

  • sza() – the SZA instance identifying the nuclide

  • mass() – the mass of the nuclide

The Nuclide class also provides all comparison operators, ordered the same as the SZA class.

Nautilus also provides the streaming operator for a Nuclide, providing a simple way to print values.

IndexedNuclide

The IndexedNuclide class is based on the ReactionIsotope class from Singe. For compatibility there is an alias called ReactionIsotope, but it is deprecated.

The IndexedNuclide class extends the Nuclide class, additionally adding an index so that information related to this nuclide can be accessed from arrays, so long as those arrays are ordered consistently. In addition to the accessors and operators provided by Nuclide, the IndexedNuclide class adds the index() accessor, which returns the index.

Zaid Tools

The zaid_tools.hpp header file provides some useful tools for parsing zaids, which are identifiers used by NDI. Some of the functionality provided by zaid_tools.hpp has been more accurately and thoroughly implemented through the EntityTag framework. EntityTag should be preferred when possible, as the tools in zaid_tools.hpp are likely to be deprecated.

This header is particularly prone to inconsistent and/or incorrect naming, as it was designed for compatibilty with legacy codes rather than based on a detailed understanding of the naming conventions and motivations behind certain formats.

The chemsym_to_zaid function accepts a string in a format known as the “chemsym” format, because it is related to (but not the same as) the IUPAC chemical symbol. It currently only handles a subset of the full chemsym format. Given a chemsym, it will return an integer with the corresponding SZA value. The names “zaid” and “SZA” were incorrectly used interchangeably when this function was initially written.

The half_reaction_zaid_to_chemsym_list function accepts a string consisting of either the products or reactants of a reaction, written in the format expected for NDI reaction zaids. It will parse the string and return a std::vector of strings in the chemsym format. In practice, this is not fully consistent with the chemsym format, because there was some early confusion about the distinction between two related formats.

The append_zaids function combines the half_reaction_zaid_to_chemsym_list and chemsym_to_zaid functions, taking a string listing the products or reactants of a reaction and returning a std::vector of SZA values, with repeated entries deduplicated.

The get_reactant_zaids function accepts an NDI reaction zaid as a string, identifies the substring with the reactants, then calls append_zaids and returns the resulting list of integer SZA values. The get_product_zaids function is the same, but it will extract and parse the list of reaction products instead of the reactants. The get_nuclide_zaids function is similar, but it returns the list of all reactants and reaction products.