Example: The TRIPOS Force Field Parameters

no.	SYBYL atom type	description
1.	C.3	carbon sp3
2.	C.2	carbon sp2
4.	C.1	carbon sp1
3.	C.ar	carbon aromatic
33.	C.cat	carbocation (C+) used in guadinium
5.	N.3	nitrogen sp3
6.	N.2	nitrogen sp2
7.	N.1	nitrogen sp1
11.	N.ar	nitrogen aromatic
28.	N.am	nitrogen amide
19.	N.pl3	nitrogen trigonal planar
31.	N.4	nitrogen sp3 positively charged
8.	O.3	oxygen sp3
9.	O.2	oxygen sp2
32.	O.co2	oxygen in carboxylate and phosphate groups
8.	O.t3p	oxygen in Transferable Intermolecular Potential (TIP3P) water model
-	-	etc.
-	-	etc.

An 'atom definition' makes use of the atom types above, but also specifies:

• valence
• geometry (tetrehedral, trigonal, linear, etc.
• equivalent atom type
• atomic number
• van der Waals radius
• default color
• formal charge
• electronegativity
• hydrogen bond affinity
• number of lone pairs
• atomic weight
• etc.

no.	SYBYL bond type	description
1	1	single bond
2	2	double bond
3	3	triple bond
4	am	amide bond
5	ar	aromatic bond
8	du	dummy bond
9	un	unknown bond (displayed)
10	nc	not connected (not displayed)

Once 'atoms' and 'bonds' are defined, huge tables with constants for every combination of 'atoms' and 'bonds' complete the definition of the Force Field.

Bond stretch parameters:

(atom1 | atom2 | bond-type | equilibrium distance | k | reference)

C.1	C.1	3	1.204	1400	JL_EST
C.1	C.1	1	1.38	700	MC_88
Br	C.2	1	1.89	500	EXP
C.1	C.2	1	1.44	1340	*
C.1	C.2	2	1.44	1340	*
C.2	C.2	2	1.335	1340	WHITE_77
C.2	C.2	1	1.47	700	MC_88
C.1	C.3	1	1.458	640	*
C.2	C.3	1	1.501	639	WHITE_75
C.3	C.3	1	1.54	633.6	*
Br	C.ar	1	1.85	500	*
C.1	C.ar	1	1.44	1340	*
C.2	C.ar	1	1.51	1340	*
C.3	C.ar	1	1.525	640	*
C.ar	C.ar	ar	1.395	1400	*
C.ar	C.ar	1	1.48	1000	*
C.2	Cl	1	1.75	520	*
C.3	Cl	1	1.767	600	*
C.ar	Cl	1	1.75	513.36	*
C.2	F	1	1.33	1200	*
C.3	F	1	1.36	600	*
C.ar	F	1	1.33	500	*
*	H	1	1.008	700	*
C.1	H	1	1.056	700	JL_EST
C.2	H	1	1.089	692	*
C.3	H	1	1.1	662.4	WHITE_77
C.ar	H	1	1.084	692	*
C.ar	I	1	2.05	490	*
C.1	N.1	3	1.158	1600	*
C.1	N.2	1	1.33	1300	*
C.1	N.2	2	1.33	1300	*
C.2	N.2	2	1.27	1305.94	*
C.2	N.2	1	1.444	1300	MC_88
C.3	N.2	1	1.44	760.2	*
C.ar	N.2	1	1.346	1305.94	*
N.2	N.2	2	1.346	1305.94	*
N.2	N.2	1	1.418	1300	MC_88
C.2	N.3	1	1.33	1300	EXP
C.3	N.3	1	1.47	760	*
C.ar	N.3	1	1.41	720	EXP
H	N.3	1	1.08	692	*
C.2	N.4	1	1.33	1300	*
C.3	N.4	1	1.47	760	*
C.ar	N.4	1	1.41	720	*
C.2	N.am	am	1.345	870.1	*
C.2	N.am	1	1.345	870.1	*
C.3	N.am	1	1.45	677.6	*
C.ar	N.am	1	1.416	1090.08	*
H	N.am	1	1	700	*
N.2	N.am	1	1.44	667.6	*
N.am	N.am	1	1.45	744.48	*
C.ar	N.ar	ar	1.346	1305.94	*
N.ar	N.ar	ar	1.33	1400	*
C.2	N.pl3	1	1.3	1200	*
C.cat	N.pl3	ar	1.3	1200	MAC91
C.3	N.pl3	1	1.45	676	*
C.ar	N.pl3	1	1.35	1306	*
H	N.pl3	1	1.03	692	*
N.2	N.pl3	1	1.35	1305.94	EXP
C.2	O.2	2	1.22	1555.2	*
C.2     O.co2   ar      1.26    699.84  MAC91
N.am	O.2	1	1.24	1120	*
N.pl3	O.2	2	1.21	680	EXP
C.2	O.3	1	1.33	699.84	*
C.3	O.3	1	1.43	618.9	*
C.ar	O.3	1	1.39	700	*
H	O.3	1	.95	1007.5	*
N.2	O.3	1	1.405	1200	*
N.pl3	O.3	1	1.4	620	EXP
O.3	O.3	1	1.48	1172.16	*
C.3	P.3	1	1.83	407.6	*
O.2	P.3	1	1.49	1400	*
O.2	P.3	2	1.49	1400	*
O.co2	P.3	ar	1.49	1400	MAC91
O.3	P.3	1	1.6	800	*
C.2	S.2	2	1.71	400	*
C.3	S.2	1	1.8	381.6	*
C.ar	S.2	1	1.74	700	*
C.2	S.3	1	1.78	360	*
C.3	S.3	1	1.817	381.6	*
C.ar	S.3	1	1.77	360	*
N.3	S.3	1	1.625	360	*
N.4	S.3	1	1.625	360	*
O.2	S.3	2	1.45	600	*
S.3	S.3	1	2.03	600	EXP
C.2	S.o	1	1.71	360	TRIPOS_86
C.3	S.o	1	1.8	381.6	TRIPOS_86
O.2	S.o	2	1.45	600	*
O.3	S.o	1	1.5	600	*
C.3	S.o2	1	1.8	381.6	TRIPOS_86
O.2	S.o2	2	1.45	600	TRIPOS_86
O.3	S.o2	1	1.5	600	*
H.spc	H.spc	1	1.633	6000	*
H.spc	O.spc	1	1	6000	*
H.t3p	H.t3p	1	1.514	6000	*
H.t3p	O.t3p	1	0.9572	6000	*
.
.
ANY	ANY	1	1.5	600	*
ANY	ANY	2	1.5	600	*
ANY	ANY	3	1.5	600	*
ANY	ANY	am	1.5	600	*
ANY	ANY	ar	1.5	600	*
ANY	ANY	du	1.5	600	*
ANY	ANY	nc	1.5	600	*
ANY	ANY	un	1.5	600	*
.
.
.

Bond angle bending parameters:

(atom1 | atom2 | atom 3 | equilibrium angle | k | reference)

*	C.1	*	180	0.04	*
C.1	C.1	C.2	180	0.04	JL_EST
C.2	C.1	N.1	180	0.04	*
C.3	C.1	N.1	180	0.04	*
C.ar	C.1	N.1	180	0.04	*
N.1	C.1	O.3	180	0.04	*
*	C.2	*	120	0.024	WHITE_77
*       C.2     O.co2   120     0.024   MAC91
*	C.cat	*	120	0.024	WHITE_77
Br	C.2	Br	120	0.02	EXP
Br	C.2	C.2	120	0.036	EXP
C.2	C.2	C.2	121.7	0.018	*
C.1	C.2	C.3	120	0.024	JL_EST
C.2	C.2	C.3	121	0.024	WHITE_77
C.3	C.2	C.3	116.4	0.046	WHITE_77
C.1	C.2	C.ar	120	0.024	*
C.2	C.2	C.ar	120	0.026	*
C.3	C.2	C.ar	120	0.024	EXP
C.ar	C.2	C.ar	120	0.024	*
C.2	C.2	Cl	120	0.036	*
C.ar	C.2	Cl	120	0.036	*
Cl	C.2	Cl	122	0.03	*
*	C.2	H	120	0.012	JL_EST
C.1	C.2	N.2	123	0.07	*
C.2	C.2	N.2	120	0.024	*
C.3	C.2	N.2	118	0.02	*
C.ar	C.2	N.2	120	0.04	*
C.2	C.2	N.3	120	0.024	*
C.3	C.2	N.3	118	0.04	EXP
N.2	C.2	N.3	121.8	0.03	EXP
N.3	C.2	N.3	116.4	0.03	EXP
C.2	C.2	N.am	120	0.024	*
C.3	C.2	N.am	117	0.02	WHITE_75
C.ar	C.2	N.am	120	0.04	*
N.2	C.2	N.am	123	0.07	*
N.am	C.2	N.am	120	0.03	*
C.2	C.2	N.pl3	120	0.024	*
C.3	C.2	N.pl3	117	0.02	EXP
N.2	C.2	N.pl3	123	0.07	EXP
C.1	C.2	O.2	120	0.06	JL_EST
C.1	C.2	O.co2 120   0.06  MAC91
C.2	C.2	O.2	120	0.026	*
C.2	C.2	O.co2 120	0.026	MAC91
C.3	C.2	O.2	120	0.026	*
C.3	C.2	O.co2	118	0.026	MAC91
C.ar	C.2	O.2	120	0.026	*
C.ar	C.2	O.co2	120	0.026	MAC91
N.3	C.2	O.2	120	0.026	EXP
N.3	C.2	O.co2	120	0.026	MAC91
N.am	C.2	O.2	123	0.03	WHITE_75
N.am	C.2	O.co2	123	0.03	MAC91
N.pl3	C.2	O.2	123	0.03	EXP
N.pl3	C.2	O.co2	123	0.03	MAC91
C.2	C.2	O.3	120	0.072	*
C.3	C.2	O.3	114	0.03	*
C.ar	C.2	O.3	120	0.03	*
N.am	C.2	O.3	110.5	0.014	*
O.2	C.2	O.3	120	0.03	*
O.co2 C.2   O.co2 124   0.03  MAC91
N.2	C.2	S.3	125.6	0.028	*
N.am	C.2	S.3	111.5	0.03	*
O.2	C.2	S.3	125	0.016	*
O.co2	C.2	S.3	125	0.016	MAC91
*	C.3	*	109.5	0.02	WHITE_77
C.2	C.3	C.2	109.5	0.018	*
C.1	C.3	C.3	109.5	0.024	*
C.2	C.3	C.3	109.5	0.018	WHITE_75
C.3	C.3	C.3	109.5	0.024	*
C.2	C.3	C.ar	109.47	0.018	*
C.3	C.3	C.ar	109.5	0.024	*
C.ar	C.3	C.ar	109.5	0.018	*
C.3	C.3	Cl	109.5	0.02	*
Cl	C.3	Cl	109.5	0.02	*
C.ar	C.3	F	110	0.024	JL_EST
F	C.3	F	109.5	0.04	*
*	C.3	H	109.5	0.016	WHITE_77
C.2	C.3	H	110	0.016	WHITE_75
H	C.3	H	109.5	0.024	WHITE_75
C.3	C.3	N.2	109.5	0.018	*
C.2	C.3	N.3	109.5	0.018	*
C.3	C.3	N.3	109.5	0.024	*
C.ar	C.3	N.3	109.5	0.018	*
C.2	C.3	N.am	109.5	0.022	*
C.3	C.3	N.am	109.5	0.018	*
C.ar	C.3	N.am	109.5	0.02	EXP
H	C.3	N.am	110	0.02	WHITE_75
N.2	C.3	N.am	109.5	0.02	EXP
N.am	C.3	N.am	109.5	0.04	*
F	C.3	N.ar	109.5	0.04	*
C.2	C.3	N.pl3	109.5	0.018	*
C.3	C.3	N.pl3	109.5	0.02	*
C.ar	C.3	N.pl3	109.5	0.02	*
C.2	C.3	O.3	109.5	0.022	*
C.3	C.3	O.3	109.5	0.022	*
C.ar	C.3	O.3	109.5	0.018	*
N.am	C.3	O.3	109.5	0.02	*
O.3	C.3	O.3	109.5	0.02	*
C.3	C.3	P.3	112	0.014	*
C.2	C.3	S.2	109.5	0.018	*
C.3	C.3	S.2	109.5	0.018	*
N.am	C.3	S.2	109.5	0.04	*
C.2	C.3	S.3	107.8	0.018	*
C.3	C.3	S.3	107.8	0.018	*
C.ar	C.3	S.3	107.8	0.018	*
N.am	C.3	S.3	109.5	0.024	JL_EST
O.3	C.3	S.3	107.8	0.02	*
*	C.ar	*	120	0.024	*
Br	C.ar	C.ar	120	0.036	*
C.2	C.ar	C.ar	120	0.024	*
C.3	C.ar	C.ar	120	0.024	*
C.ar	C.ar	C.ar	120	0.024	*
C.ar	C.ar	Cl	120	0.036	*
C.ar	C.ar	F	120	0.036	*
C.ar	C.ar	I	120	0.036	*
C.3	C.ar	N.2	120	0.04	*
C.ar	C.ar	N.2	120	0.04	*
N.2	C.ar	N.2	120	0.04	*
C.ar	C.ar	N.3	120	0.062	EXP
C.ar	C.ar	N.am	120	0.062	*
N.2	C.ar	N.am	118	0.04	*
N.am	C.ar	N.am	120	0.03	*
C.2	C.ar	N.ar	120	0.04	EXP
C.3	C.ar	N.ar	120	0.04	EXP
C.ar	C.ar	N.ar	120	0.024	EXP
N.am	C.ar	N.ar	118	0.04	EXP
C.3	C.ar	N.pl3	120	0.04	*
C.ar	C.ar	N.pl3	120	0.04	*
N.2	C.ar	N.pl3	120	0.04	*
N.am	C.ar	N.pl3	120	0.04	*
N.pl3	C.ar	N.pl3	120	0.04	*
C.3	C.ar	O.3	120	0.04	*
C.ar	C.ar	O.3	120	0.062	*
C.ar	C.ar	S.2	120	0.062	*
C.ar	C.ar	S.3	120	0.062	*
*	N.1	*	180	0.08	*
*	N.2	*	120	0.04	*
C.1	N.2	C.2	120	0.04	*
C.2	N.2	C.2	123	0.08	EXP
C.2	N.2	C.3	110	0.082	*
C.2	N.2	C.ar	123	0.08	*
C.3	N.2	C.ar	110	0.082	*
C.ar	N.2	C.ar	120	0.04	*
C.2	N.2	N.2	112	0.044	*
C.3	N.2	N.2	118	0.04	*
C.ar	N.2	N.2	118	0.04	*
C.2	N.2	N.am	120	0.044	EXP
C.2	N.2	N.pl3	120	0.044	EXP
C.2	N.2	O.3	105	0.044	EXP
*	N.3	*	109.5	0.04	*
C.2	N.3	C.3	110	0.04	EXP
C.3	N.3	C.3	109.5	0.018	*
C.3	N.3	C.ar	118	0.04	EXP
C.ar	N.3	C.ar	118	0.04	EXP
C.3	N.3	S.2	109.5	0.04	*
*	N.4	*	109.5	0.01	TRIPOS_86
C.3	N.4	C.3	109.5	0.018	*
*	N.am	*	120	0.02	*
C.2	N.am	C.2	120	0.018	*
C.2	N.am	C.3	118	0.044	*
C.3	N.am	C.3	122	0.04	*
C.2	N.am	C.ar	120	0.052	*
C.3	N.am	C.ar	118	0.044	*
C.ar	N.am	C.ar	120	0.044	*
C.2	N.am	H	119	0.016	WHITE_75
C.3	N.am	H	117	0.02	WHITE_75
C.2	N.am	N.2	120	0.018	EXP
C.3	N.am	N.2	120	0.024	*
C.ar	N.am	N.2	109.5	0.044	*
C.2	N.am	N.am	120	0.018	*
C.3	N.am	N.am	120	0.024	*
C.ar	N.am	N.am	120	0.052	*
C.2	N.am	O.2	120	0.024	*
C.3	N.am	O.2	120	0.02	*
C.ar	N.am	O.2	120	0.024	*
O.2	N.am	O.2	120	0.02	*
*	N.ar	*	120	0.02	*
C.ar	N.ar	C.ar	120	0.04	EXP
*	N.pl3	*	120	0.04	*
C.2	N.pl3	C.2	120	0.04	EXP
C.2	N.pl3	C.ar	120	0.04	EXP
C.3	N.pl3	C.ar	120	0.04	*
C.ar	N.pl3	C.ar	120	0.04	*
C.2	N.pl3	N.2	120	0.018	EXP
C.ar	N.pl3	N.2	120	0.018	EXP
C.2	N.pl3	O.2	112	0.04	EXP
O.2	N.pl3	O.2	127	0.06	EXP
*	O.3	*	109.5	0.02	*
C.2	O.3	C.2	110	0.02	*
C.2	O.3	C.3	109.5	0.044	*
C.3	O.3	C.3	109.5	0.044	*
C.2	O.3	C.ar	110	0.02	*
C.3	O.3	C.ar	110	0.02	*
C.ar	O.3	C.ar	110	0.02	*
C.2	O.3	N.2	108.5	0.044	EXP
C.3	O.3	O.3	103.9	0.094	*
C.3	O.3	P.3	120	0.01	*
H	O.3	H	104.5	0.02	MC90
*	P.3	*	109.5	0.02	*
O.2	P.3	O.2	109.5	0.02	*
Du	P.3	O.3	109.5	0.014	*
O.2	P.3	O.3	109.5	0.02	*
O.3	P.3	O.3	109.5	0.02	*
*	S.2	*	110	0.04	*
C.3	S.2	N.3	111	0.04	*
C.ar	S.2	N.3	111	0.04	*
*	S.3	*	97	0.02	*
C.2	S.3	C.3	94.3	0.022	*
C.3	S.3	C.3	98	0.02	*
C.ar	S.3	C.ar	97.5	0.062	*
C.3	S.3	S.3	102.9	0.06	EXP
*	S.o	O.2	107	0.04	TRIPOS_86
*	S.o2	O.2	107	0.04	TRIPOS_86
O.2	S.o2	O.2	118	0.04	TRIPOS_86
H.spc	H.spc	O.spc	35.265	1.0	*
H.spc	O.spc	H.spc	109.47	1.0	*
H.t3p	H.t3p	O.t3p	37.74	1.0	*
H.t3p	O.t3p	H.t3p	104.52	1.0	*

Torsion parameters:

(atom1 | atom2 | atom 3 | atom 4 | bond type | k | periodicity | reference)

*	C.1	C.1	*	3	0	1	JL_EST
*	C.1	C.1	*	1	0	1	*
*	C.1	C.2	*	1	0	1	*
*	C.1	C.2	*	2	0	1	*
*	C.2	C.2	*	2	12.5	-2	WHITE_77
*	C.2	C.2	*	1	1.424	-2	*
*	C.2	C.cat	*	1	1.424	-2	*
*	C.1	C.3	*	1	0	1	*
*	C.2	C.3	*	1	.12	-3	*
*	C.2	C.3	C.2	1	.126	3	WHITE_77
*	C.2	C.3	C.3	1	.126	3	WHITE_77
*	C.2	C.3	H	1	.274	3	WHITE_77
O.2	C.2	C.3	C.3	1	.7	-3	JL_EST
O.co2	C.2	C.3	C.3	1	.7	-3	MAC91
*	C.3	C.3	*	1	.2	3	*
C.2	C.3	C.3	C.2	1	0.04	3	WHITE_77
C.2	C.3	C.3	C.3	1	.126	3	WHITE_77
C.3	C.3	C.3	C.3	1	.5	3	MC_88
*	C.3	C.3	H	1	.32	3	MC_88
*	C.1	C.ar	*	1	0	1	*
*	C.2	C.ar	*	1	1.6	-2	*
*	C.3	C.ar	*	1	.12	-3	*
*	C.ar	C.ar 	C.ar	ar	2.35	-2	MCAROM
*	C.ar	C.ar	*	ar	2	-2	*
*	C.ar	C.ar	*	1	.6	-2	*
*	C.1	N.2	*	1	0	1	*
*	C.1	N.2	*	2	0	1	*
*	C.2	N.2	*	2	12	-2	*
*	C.2	N.2	*	1	12	-2	*
*	C.3	N.2	*	1	.4	-3	*
*	C.ar	N.2	*	1	1.6	-2	*
*	N.2	N.2	*	2	1.6	-2	*
*	N.2	N.2	*	1	1.6	-2	*
*	C.2	N.3	*	1	.12	-3	*
*	C.3	N.3	*	1	.2	3	*
*	C.ar	N.3	*	1	.12	-3	*
*	N.3	N.3	*	1	.2	3	*
*	C.2	N.am	*	am	6.46	-2	*
*	C.2	N.am	*	1	6.46	-2	*
*	C.3	N.am	*	1	.2	3	*
*	C.ar	N.am	*	1	1.6	-2	*
*	N.2	N.am	*	1	1.6	-2	*
*	N.3	N.am	*	1	.12	-3	*
*	N.am	N.am	*	1	1.6	-2	*
*	C.ar	N.ar	*	ar	1.6	-2	EXP
*	C.2	N.pl3	*	1	12	-2	*
*	C.cat	N.pl3	*	ar	12	-2	MAC91
*	C.3	N.pl3	*	1	.4	-3	*
*	C.ar	N.pl3	*	1	1.6	-2	*
*	N.2	N.pl3	*	1	1.6	-2	*
*	N.pl3	N.pl3	*	1	1.6	-2	*
*	C.2	O.3	*	1	5.8	-2	*
*	C.3	O.3	*	1	1.2	3	*
*	C.ar	O.3	*	1	1.2	-2	*
*	N.2	O.3	*	1	1	2	EXP
*	N.3	O.3	*	1	.2	3	*
*	C.2	P.3	*	1	1	-2	*
*	C.3	P.3	*	1	.4	3	*
*	C.ar	P.3	*	1	1	3	*
*	O.3	P.3	*	1	.4	3	*
*	C.2	S.2	*	2	1	-2	*
*	C.3	S.2	*	1	.4	3	*
*	C.ar	S.2	*	1	1	3	*
*	N.3	S.2	*	1	.4	3	*
*	C.2	S.3	*	1	1	-2	*
*	C.3	S.3	*	1	.4	3	*
*	C.ar	S.3	*	1	1	3	*
*	S.3	S.3	*	1	6.75	2	EXP
C.2	C.2	C.3	C.2	1	.126	-3	WHITE_77
C.2	C.2	C.3	H	1	.273	-3	WHITE_77
C.3	C.2	C.3	C.2	1	.126	3	WHITE_77
C.3	C.2	C.3	C.3	1	.126	3	WHITE_77
C.3	C.2	C.3	H	1	.274	3	WHITE_77
H	C.2	C.3	C.2	1	.274	3	WHITE_77
H	C.2	C.3	C.3	1	.274	3	WHITE_77
H	C.2	C.3	H	1	.274	3	WHITE_77
C.2	C.2	C.3	*	1	.126	-3	WHITE_77
C.3	C.2	C.3	*	1	.126	3	WHITE_77
H	C.2	C.3	*	1	.274	3	WHITE_77
C.2	C.2	C.3	C.3	1	.126	-3	WHITE_77