function [Z,w] = strtoz(s)
Return atomic numbers Z and the corresponding number of elements w
in the compound.
Input s is either a string containing the name of the
compound or the atomic number Z.
If s is a string matrix the compounds are read rowwise and the outputs
Z and w are matrices whose rows correspond to the compounds read from
the rows of s.
in:
s = string containing the stoichiometry of the compound (eg. AlO3)
or atomic number Z
out:
Z = vector containing the atomic numbers of the elements in compound s
w = number atoms of each element Z of the compound