Support : Dialog Search Aids : Chemical Indexing Fields in Inspec

Chemical Indexing Fields in Inspec®
(Dialog File 2)

Information about inorganic chemical substances and material systems is indexed and searchable using the CI= prefix for all records added to File 2 since January 1987. The chemical indexing fields are structured so that both the substance or substances being searched and their role (e.g., as dopant, substrate, or part of an interface system) can be specified. Chemical indexing is not used for organic materials because the organic compounds mentioned in Inspec are typically simple ones, are usually indexed by name (e.g., "anthracene") rather than formula, and occur in contexts that do not involve the complexities of the inorganic systems covered by Inspec that make chemical indexing useful.

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Roles

For each substance or material system, entries in the Chemical Indexing (CI=) field include the substance or system terms and their components down to the level of individual elements. Each index term is associated with a role indicator that describes the role played by the material system or element in the format CI = ITEM ROLE, for example, CI = GAAS BIN for gallium arsenide as a binary system. Each entry is indexed and searchable both as a complete phrase and using proximity operators, e.g., SELECT CI=GAAS BIN or SELECT CI = (GAAS(W)BIN). Within Inspec bibliographic records the chemical indexing sections show the terms relating to a particular substance or system in a single subfield, with each term (item plus role, i.e. Ga/bin) separated from the next by a space, a hyphen, and another space, e.g., GaAs/bin - InAs/bin - As/bin - Ga/bin - In/bin.

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Items

An "item" is a chemical substance, a material system, or a component of a substance or system. The standard one- or two-character symbols are used for the chemical elements, including the symbols D (deuterium) and T (tritium) for the hydrogen isotopes. A "role" describes the role the item plays in the complete substance or system, or the type of system in the entry for the complete system.

Searchable Roles. The following roles are searchable:

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Indexing Levels

Chemical substances and material systems are indexed in the CI= field at the following levels:

1. The complete substance or system with its role, e.g., AL-SIO2 INT.
2. Any substances or material subsystems contained in a system, with their roles, e.g., SIO2 INT, AL INT, O2 INT, SI INT, O INT, SIO2 BIN, O2 BIN, SI BIN, O BIN, AL EL. In this example, each component is given two role codes, one for its role as part of an interface system and one describing it as a separate system (multiple-element or single-element respectively) in itself.
3. Any recognized chemical groups such as niobates (NBO3), carbonates (CO3), or nitrates (NO3), with their roles, e.g. NBO3 INT and NBO3 SS. For more information, see IET Inspec Chemical Indexing manual.
4. Chemical elements with any definite numbers (integer or decimal only) associated with composition and their roles, e.g. O3 INT and O3 SS.

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Sample Record

An example of an Inspec record with chemical indexing is shown below:

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Search Tips

Only records added to Inspec since February 1987 have chemical indexing; in earlier references chemical substances and systems must be searched in the Identifier field.

• General Searching. To search for an element in any form, as an element or part of a larger system, SELECT the element symbol without specifying a role, e.g., SELECT CI=RB. This method may retrieve irrelevant references when a two-character element symbol is also the formula of a binary compound; for example, SELECT CI=CO retrieves references both to the element cobalt and the compound carbon monoxide. These irrelevant references may be eliminated using the (NOT S) operator, e.g., SELECT CI = (CO(NOT S)C(W)BIN) to retrieve references on Cobalt and eliminate those on carbon monoxide. Role codes may be used to search for elements occurring in particular roles. For example, SELECT CI = SI EL retrieves references to elemental silicon, and SELECT CI = SI DOP retrieves references in which silicon occurs as a dopant. SELECT CI = GA BIN retrieves all references to binary compounds or alloys containing gallium, SELECT CI= GA SS retrieves all gallium compounds or alloys with 3 or more components, SELECT CI= (GA BIN OR GA SS) retrieves all gallium compounds or alloys containing gallium.



• Specific Compounds. To search for specific compounds, SELECT the symbols or formulas for the individual components (elements or recognized chemical groups) with appropriate roles linked together using the (S) operator, e.g.,

• Chemical Notations. When the chemical notation for a particular compound is known to be standardized, it is also possible to SELECT the complete formula directly, e.g., SELECT CI = GAAS BIN; SELECT CI = CUSO4 (except in cases of possible ambiguity such as carbon monoxide); SELECT CI="GAAS:CR INT". (Note that the colon (:) denoting a dopant must be masked by quotation marks.) However, notation is not standardized for many systems of interest; for example, gallium aluminum arsenide may appear as CI = GAALAS, CI = ALGAAS. In these cases the (S) operator must be used for comprehensive retrieval.



• Compounds or Systems. When searching for compounds or systems with 3 or more components (role code SS) using the (S) operator, irrelevant references may be retrieved to substances containing other elements in addition to those specified in the search. For example, the above search for gallium aluminum arsenide also retrieves references to gallium aluminum arsenide phosphide. Such irrelevant references, if known, may be eliminated using the (NOT S) operator, e.g.,


SELECT CI = (AL SS(S)GA SS(S)AS SS(NOT S)P)


• Elements or Chemical Groups. To search for an element or chemical group occurring in an interface system, SELECT that component with the role code "INT; " for example, SELECT CI = SI INT for interfaces involving silicon or its compounds or alloys. The search SELECT CI = (SI INT(S)SI EL) limits retrieval to interfaces involving elemental silicon. To search for specific interfaces, search the Chemical Indexing field for all components with the role code INT, and again with the role codes EL, BIN, SS, or DOP as appropriate, linking all terms with the (S) operator. For example, the following search retrieves references to GaAs-GaAlAs interfaces:




S CI=(GA INT(S)AL INT(S)AS INT(S)GA BIN(S)AS BIN(S)GA SS(S)AL SS(S)AS SS)