Greek letters and special symbols
A limited number of special characters (such as Greek letters, sub- and superscripts, and a few others) may be indicated in CIF text for typesetting purposes, using the special codes listed below.
Greek letters
In general, the corresponding letter of the Latin alphabet, prefixed by a backslash character. The complete set is:
α | Α | \a | \A | alpha |
β | Β | \b | \B | beta |
χ | Χ | \c | \C | chi |
δ | Δ | \d | \D | delta |
ε | Ε | \e | \E | epsilon |
φ | Φ | \f | \F | phi |
γ | Γ | \g | \G | gamma |
η | Η | \h | \H | eta |
ι | Ι | \i | \I | iota |
κ | Κ | \k | \K | kappa |
λ | Λ | \l | \L | lambda |
μ | Μ | \m | \M | mu |
ν | Ν | \n | \N | nu |
ο | Ο | \o | \O | omicron |
π | Π | \p | \P | pi |
θ | Θ | \q | \Q | theta |
ρ | Ρ | \r | \R | rho |
σ | Σ | \s | \S | sigma |
τ | Τ | \t | \T | tau |
υ | Υ | \u | \U | upsilon |
ω | Ω | \w | \W | omega |
ξ | Ξ | \x | \X | xi |
ψ | Ψ | \y | \Y | psi |
ζ | Ζ | \z | \Z | zeta |
Accented letters
Accents should be indicated by using the following codes before the letter to be modified (i.e. use \'e for an acute e):
\' | acute (é) | \" | umlaut (ü) | \= | overbar |
\` | grave (à) | \~ | tilde (ñ) | \. | overdot |
\^ | circumflex (â) | \; | ogonek | \< | hacek |
\, | cedilla (ç) | \> | Hungarian umlaut | \( | breve |
Other characters
Other special alphabetic characters should be indicated as follows:
\%a | a-ring (å) | \?i | dotless i | \&s | German "ss" (ß) |
\/o | o-slash (ø) | \/l | Polish l () | \/d | barred d |
Capital letters may also be used in these codes, so an ångström symbol (Å) may be given as \%A.
Superscripts and subscripts should be indicated by bracketing relevant characters with circumflex or tilde characters, thus:
superscripts | Csp^3^ | for | Csp3 |
subscripts | U~eq~ | for | Ueq |
The closing symbol is essential to return to normal text.
Other codes are also recognized by the IUCr software. These are:
\% | degree (°) | \\times | × |
-- | dash | +- | ± |
--- | single bond | -+ | |
\\db | double bond | \\square | square |
\\tb | triple bond | \\neq | |
\\ddb | delocalized double bond | \\rangle | |
\\sim | \\langle | ||
(N.B. ~ is the code for subscript) | \\rightarrow | ||
\\simeq | \\leftarrow | ||
\\infty |
Note that \\db, \\tb and \\ddb should always be followed by a space, e.g. C=C is denoted by C\\db C.