Table 3.

PB atomic cavity radii (Å) and atom types.

Atom type	PB radius	Description
h1	0.421	H bonded to aliphatic carbon with 1 electrwd. group
h2	0.327	H bonded to aliphatic carbon with 2 electrwd. group
h4	0.577	H bonded to non-sp3 carbon with 1 electrwd. group
h5	2.021	H bonded to non-sp3 carbon with 2 electrwd. group
ha	0.735	H bonded to aromatic carbon
hc	0.753	H bonded to aliphatic carbon without electrwd. group
hn	0.681	H bonded to nitrogen atoms
ho	0.000	Hydroxyl group
o	1.117	Oxygen with one connected atom
oh	1.293	Oxygen in hydroxyl group
os	1.094	Ether and ester oxygen
c	1.200	Sp2 C carbonyl group
c1	1.139	Sp C
c2	1.200	Sp2 C
c3	1.181	Sp3 C
ca	1.139	Sp2 C in pure aromatic systems
cc	1.139	Sp2 carbons in non-pure aromatic systems
cd	1.139	Sp2 carbons in non-pure aromatic systems, identical to cc
ce	1.139	Inner Sp2 carbons in conjugated systems
cf	1.139	Inner Sp2 carbons in conjugated systems, identical to ce
cp	1.139	Head Sp2 C that connect two rings in biphenyl sys.
n	1.114	Sp2 nitrogen in amide groups
n1	1.114	Sp N
n2	1.114	Aliphatic Sp2 N with two connected atoms
n3	1.114	Sp3 N with three connected atoms
na	1.114	Sp2 N with three connected atoms
nb	1.114	Sp2 N in pure aromatic systems
nc	1.114	Sp2 N in non-pure aromatic systems
nd	1.114	Sp2 N in non-pure aromatic systems, identical to nc
nh	1.114	Amine N connected one or more aromatic rings
no	1.114	Nitro N
s	2.210	S with one connected atom
sh	2.210	Sp3 S connected with hydrogen
ss	2.210	S with one connected atom
p5	1.514	Phosphate with four connected atoms, such as O P(OH)3
py	1.514	Special p5 in conjugated system
f	1.612	Fluorine
cl	2.488	Chlorine
br	2.616	Bromine