Volume 1 Chapter 6 Summary of Connectivity Search Test Instructions
The new element symbol can be one or two alphabetic characters but cannot be a conventional element symbol, element group symbol or a symbol already defined by an ELDEF instruction.
In the example below the ELDEF instruction defines the new element symbol RR to be S or Se or Te.
T1 *CONN ELDEF RR= S, SE, TE AT1 7A 1 AT2 C 3 AT3 C 2 AT4 C 2 AT5 C 3 AT6 C 2 AT7 C 2 AT8 RR 1 DEFB 5 BO 1 2 1 BO 2 3 BO 3 4 BO 4 5 BO 5 6 BO 6 7 BO 7 2 BO 5 8 1 END QUES T1
Note that the ELDEF instruction for an element symbol must appear before the atom property record in which the symbol is used.
A few examples will illustrate the syntax of ELDEF instructions:
Ex.1
ELDEF MM = V Cr mn
The new element symbol MM is defined tobe V or Cr or Mn.
The set of old element symbols can be separated by blanks or commas.
The = sign is mandatory and no distinction is made between upper- and lower-case.
Ex.2 The element group symbol 6A covers O, S, Se, Te, Po.
Thus an alternative but equivalent definition of RR (see above) would be:
ELDEF RR = 6A - O,Po
When the negative sign is used in an ELDEF instruction the program checks to ensure that negated elements are contained within the positive set.
Thus, for example, ELDEF RR = 6A - F would be invalid.
Ex.3
ELDEF NS = 1A 2A ELDEF NT = NS - BA
This illustrates that already defined new element symbols can be used to define further new element symbols.
An equivalent single instruction would be:
ELDEF Nu = 1A, 2A - Ba
Ex.4
ELDEF PP = - TR
The new element symbol PP is defined to be not a transition element.
The value of mca specifies the minimum number of atoms, excluding terminal H atoms, connected to atom p.
The specification of the minimum number rather than the exact number allows us flexibility in defining the degree of substitution at a particular atom.
Consider the search fragment below, with the associated search question and target structures (a)-(c).
T1 *CONN AT1 TR 4 AT2 N 1 AT3 N 1 AT4 N 1 AT5 N 1 BO 1 2 BO 1 3 BO 1 4 BO 1 5 END QUES T1
Ex. A search using test T1 will register hits for (a), (b), (c), etc.
