National Institute of Standards and Technology

Computational Chemistry Comparison and Benchmark DataBase
Release
NIST Standard Reference Database 101

I	Introduction
II	Experimental data
III	Calculated data
IV	Data comparisons
V	Cost comparisons
VI	Input and output files
VII	Tutorials and Units
VIII	Links to other sites
IX	Feedback
X	Older CCCBDB versions
XII	Geometries
XIII	Vibrations
XIV	Reaction data
XV	Entropy data
XVI	Bibliographic data
XVII	Ion data
XVIII	Bad calculations
XIX	Index of properties
XX	H-bond dimers
XXI	Oddities

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The National Institute of Standards and Technology (NIST) is an agency of the U.S. Department of Commerce.

Please send questions, comments, corrections, additions and suggestions to cccbdb@nist.gov.

I.B.1.d.3.

List of Similar species

A list of homologous species, species with similar chemical groups, and isovalent or isoelectronic species.

Examples

For CH₄ homologous species are SiH₄ and CD₄.
For CH₃CH₂OH species with similar chemical groups are CH₃(CH₂)₂OH, CH₃(CH₂)₃OH, and CH₃(CH₂)₄OH.
For CH₃OH isovalent species include CH₃CH₃, NH₂NH₂, HOOH, and Cl₂,
and isoelectronic species include SiH₄, CH₃NH₂, H₂O₂, CH₃F.
Enter Formula

Rules for chemical formula

• Enter a sequence of element symbols followed by numbers to specify the amounts of desired elements (e.g., C6H6).
• Elements may be in any order.
• If only one of a given atom is desired, you may omit the number after the element symbol.
• Parentheses may be used to group atoms.
• Multiple specifications for an atom will be added. This means that CH3(CH2)4CH3 will be treated the same as C6H14.
• A comma delimited list of several species may be entered.
• Ions are indicated by placing + or - at the end of the formula (CH3+, BF4-, CO3--)

Species in the CCCBDB

• Mostly atoms with atomic number less than than 36 (Krypton), except for most of the transition metals. See section I.B.1 for a periodic table view.
• Six or fewer heavy atoms and twenty or fewer total atoms. Exception: Versions 8 and higher have a few substituted benzenes with more than six heavy atoms. Versions 12 and higher have bromine-containing molecules.