Force_field_params OPLSAA

Questions
#1

intput file:
$rem
JOBTYPE = opt
METHOD = pbe0
BASIS = aug-cc-pVDZ
QM_MM_INTERFACE = oniom
SCF_MAX_CYCLES 100000
GEOM_OPT_MAX_CYCLES 100000
FORCE_FIELD = oplsaa
USER_CONNECT = true
MOLDEN_FORMAT = true
GEOM_OPT_DRIVER = OPTIMIZE
$end

$molecule
0 1
C 3.525 0.000 0.000 11 3 0 0 0
C 3.313 1.206 2.132 11 3 4 27 0
C 3.525 0.000 1.421 11 1 2 194 0
C 3.313 1.206 3.553 11 2 5 29 0
C 3.525 0.000 4.263 11 4 7 196 0
C 3.313 1.206 6.395 11 7 8 31 0
C 3.525 0.000 5.684 11 5 6 198 0
C 3.313 1.206 7.816 11 6 9 33 0
C 3.525 0.000 8.526 11 8 11 200 0
C 3.313 1.206 10.658 11 11 12 35 0
C 3.525 0.000 9.947 11 9 10 202 0
C 3.313 1.206 12.079 11 10 13 37 0
C 3.525 0.000 12.789 11 12 15 204 0
C 3.313 1.206 14.921 11 15 16 39 0
C 3.525 0.000 14.210 11 13 14 206 0
C 3.313 1.206 16.342 11 14 17 41 0
C 3.525 0.000 17.052 11 16 19 208 0
C 3.313 1.206 19.184 11 19 20 43 0
C 3.525 0.000 18.473 11 17 18 210 0
C 3.313 1.206 20.605 11 18 21 45 0
C 3.525 0.000 21.315 11 20 23 212 0
C 3.313 1.206 23.447 11 23 24 47 0
C 3.525 0.000 22.736 11 21 22 214 0
C 3.313 1.206 24.868 11 22 0 0 0
C 2.701 2.266 0.000 11 27 0 0 0
C 1.763 3.053 2.132 11 27 28 51 0
C 2.701 2.266 1.421 11 2 25 26 0
C 1.763 3.053 3.553 11 26 29 53 0
C 2.701 2.266 4.263 11 4 28 31 0
C 1.763 3.053 6.395 11 31 32 55 0
C 2.701 2.266 5.684 11 6 29 30 0
C 1.763 3.053 7.816 11 30 33 57 0
C 2.701 2.266 8.526 11 8 32 35 0
C 1.763 3.053 10.658 11 35 36 59 0
C 2.701 2.266 9.947 11 33 10 34 0
C 1.763 3.053 12.079 11 34 37 61 0
C 2.701 2.266 12.789 11 12 36 39 0
C 1.763 3.053 14.921 11 39 40 63 0
C 2.701 2.266 14.210 11 14 37 38 0
C 1.763 3.053 16.342 11 38 41 65 0
C 2.701 2.266 17.052 11 16 40 43 0
C 1.763 3.053 19.184 11 43 44 67 0
C 2.701 2.266 18.473 11 18 41 42 0
C 1.763 3.053 20.605 11 42 45 69 0
C 2.701 2.266 21.315 11 20 44 47 0
C 1.763 3.053 23.447 11 47 48 71 0
C 2.701 2.266 22.736 11 22 45 46 0
C 1.763 3.053 24.868 11 46 0 0 0
C 0.612 3.472 0.000 11 51 0 0 0
C -0.612 3.472 2.132 11 51 52 75 0
C 0.612 3.472 1.421 11 50 26 49 0
C -0.612 3.472 3.553 11 50 53 77 0
C 0.612 3.472 4.263 11 52 28 55 0
C -0.612 3.472 6.395 11 55 56 79 0
C 0.612 3.472 5.684 11 54 30 53 0
C -0.612 3.472 7.816 11 54 57 81 0
C 0.612 3.472 8.526 11 56 32 59 0
C -0.612 3.472 10.658 11 59 60 83 0
C 0.612 3.472 9.947 11 58 57 34 0
C -0.612 3.472 12.079 11 58 61 85 0
C 0.612 3.472 12.789 11 60 36 63 0
C -0.612 3.472 14.921 11 63 64 87 0
C 0.612 3.472 14.210 11 62 38 61 0
C -0.612 3.472 16.342 11 62 65 89 0
C 0.612 3.472 17.052 11 64 40 67 0
C -0.612 3.472 19.184 11 67 68 91 0
C 0.612 3.472 18.473 11 66 42 65 0
C -0.612 3.472 20.605 11 66 69 93 0
C 0.612 3.472 21.315 11 68 44 71 0
C -0.612 3.472 23.447 11 71 72 95 0
C 0.612 3.472 22.736 11 70 46 69 0
C -0.612 3.472 24.868 11 70 0 0 0
C -1.763 3.053 0.000 11 75 0 0 0
C -2.701 2.266 2.132 11 75 76 99 0
C -1.763 3.053 1.421 11 50 73 74 0
C -2.701 2.266 3.553 11 74 77 101 0
C -1.763 3.053 4.263 11 52 76 79 0
C -2.701 2.266 6.395 11 79 80 103 0
C -1.763 3.053 5.684 11 54 77 78 0
C -2.701 2.266 7.816 11 78 81 105 0
C -1.763 3.053 8.526 11 56 80 83 0
C -2.701 2.266 10.658 11 83 84 107 0
C -1.763 3.053 9.947 11 81 58 82 0
C -2.701 2.266 12.079 11 82 85 109 0
C -1.763 3.053 12.789 11 60 84 87 0
C -2.701 2.266 14.921 11 87 88 111 0
C -1.763 3.053 14.210 11 62 85 86 0
C -2.701 2.266 16.342 11 86 89 113 0
C -1.763 3.053 17.052 11 64 88 91 0
C -2.701 2.266 19.184 11 91 92 115 0
C -1.763 3.053 18.473 11 66 89 90 0
C -2.701 2.266 20.605 11 90 93 117 0
C -1.763 3.053 21.315 11 68 92 95 0
C -2.701 2.266 23.447 11 95 96 119 0
C -1.763 3.053 22.736 11 70 93 94 0
C -2.701 2.266 24.868 11 94 0 0 0
C -3.313 1.206 0.000 11 99 0 0 0
C -3.525 0.000 2.132 11 99 100 123 0
C -3.313 1.206 1.421 11 74 97 98 0
C -3.525 0.000 3.553 11 98 101 125 0
C -3.313 1.206 4.263 11 76 100 103 0
C -3.525 0.000 6.395 11 103 104 127 0
C -3.313 1.206 5.684 11 78 101 102 0
C -3.525 0.000 7.816 11 102 105 129 0
C -3.313 1.206 8.526 11 80 104 107 0
C -3.525 0.000 10.658 11 107 108 131 0
C -3.313 1.206 9.947 11 105 82 106 0
C -3.525 0.000 12.079 11 106 109 133 0
C -3.313 1.206 12.789 11 84 108 111 0
C -3.525 0.000 14.921 11 111 112 135 0
C -3.313 1.206 14.210 11 86 109 110 0
C -3.525 0.000 16.342 11 110 113 137 0
C -3.313 1.206 17.052 11 88 112 115 0
C -3.525 0.000 19.184 11 115 116 139 0
C -3.313 1.206 18.473 11 90 113 114 0
C -3.525 0.000 20.605 11 114 117 141 0
C -3.313 1.206 21.315 11 92 116 119 0
C -3.525 0.000 23.447 11 119 120 143 0
C -3.313 1.206 22.736 11 94 117 118 0
C -3.525 0.000 24.868 11 118 0 0 0
C -3.313 -1.206 0.000 11 123 0 0 0
C -2.701 -2.266 2.132 11 123 124 147 0
C -3.313 -1.206 1.421 11 121 122 98 0
C -2.701 -2.266 3.553 11 122 125 149 0
C -3.313 -1.206 4.263 11 124 100 127 0
C -2.701 -2.266 6.395 11 127 128 151 0
C -3.313 -1.206 5.684 11 125 126 102 0
C -2.701 -2.266 7.816 11 126 129 153 0
C -3.313 -1.206 8.526 11 128 104 131 0
C -2.701 -2.266 10.658 11 131 132 155 0
C -3.313 -1.206 9.947 11 129 130 106 0
C -2.701 -2.266 12.079 11 130 133 157 0
C -3.313 -1.206 12.789 11 132 108 135 0
C -2.701 -2.266 14.921 11 135 136 159 0
C -3.313 -1.206 14.210 11 133 134 110 0
C -2.701 -2.266 16.342 11 134 137 161 0
C -3.313 -1.206 17.052 11 136 112 139 0
C -2.701 -2.266 19.184 11 139 140 163 0
C -3.313 -1.206 18.473 11 137 138 114 0
C -2.701 -2.266 20.605 11 138 141 165 0
C -3.313 -1.206 21.315 11 140 116 143 0
C -2.701 -2.266 23.447 11 143 144 167 0
C -3.313 -1.206 22.736 11 141 142 118 0
C -2.701 -2.266 24.868 11 142 0 0 0
C -1.763 -3.053 0.000 11 147 0 0 0
C -0.612 -3.472 2.132 11 147 148 171 0
C -1.763 -3.053 1.421 11 122 145 146 0
C -0.612 -3.472 3.553 11 146 149 173 0
C -1.763 -3.053 4.263 11 124 148 151 0
C -0.612 -3.472 6.395 11 151 152 175 0
C -1.763 -3.053 5.684 11 126 149 150 0
C -0.612 -3.472 7.816 11 150 153 177 0
C -1.763 -3.053 8.526 11 128 152 155 0
C -0.612 -3.472 10.658 11 155 156 179 0
C -1.763 -3.053 9.947 11 153 130 154 0
C -0.612 -3.472 12.079 11 154 157 181 0
C -1.763 -3.053 12.789 11 132 156 159 0
C -0.612 -3.472 14.921 11 159 160 183 0
C -1.763 -3.053 14.210 11 134 157 158 0
C -0.612 -3.472 16.342 11 158 161 185 0
C -1.763 -3.053 17.052 11 136 160 163 0
C -0.612 -3.472 19.184 11 163 164 187 0
C -1.763 -3.053 18.473 11 138 161 162 0
C -0.612 -3.472 20.605 11 162 165 189 0
C -1.763 -3.053 21.315 11 140 164 167 0
C -0.612 -3.472 23.447 11 167 168 191 0
C -1.763 -3.053 22.736 11 142 165 166 0
C -0.612 -3.472 24.868 11 166 0 0 0
C 0.612 -3.472 0.000 11 171 0 0 0
C 1.763 -3.053 2.132 11 171 172 195 0
C 0.612 -3.472 1.421 11 146 169 170 0
C 1.763 -3.053 3.553 11 170 173 197 0
C 0.612 -3.472 4.263 11 148 172 175 0
C 1.763 -3.053 6.395 11 175 176 199 0
C 0.612 -3.472 5.684 11 150 173 174 0
C 1.763 -3.053 7.816 11 174 177 201 0
C 0.612 -3.472 8.526 11 152 176 179 0
C 1.763 -3.053 10.658 11 179 180 203 0
C 0.612 -3.472 9.947 11 154 177 178 0
C 1.763 -3.053 12.079 11 178 181 205 0
C 0.612 -3.472 12.789 11 156 180 183 0
C 1.763 -3.053 14.921 11 183 184 207 0
C 0.612 -3.472 14.210 11 158 181 182 0
C 1.763 -3.053 16.342 11 182 185 209 0
C 0.612 -3.472 17.052 11 160 184 187 0
C 1.763 -3.053 19.184 11 187 188 211 0
C 0.612 -3.472 18.473 11 162 185 186 0
C 1.763 -3.053 20.605 11 186 189 213 0
C 0.612 -3.472 21.315 11 164 188 191 0
C 1.763 -3.053 23.447 11 191 192 215 0
C 0.612 -3.472 22.736 11 166 189 190 0
C 1.763 -3.053 24.868 11 190 0 0 0
C 2.701 -2.266 0.000 11 195 0 0 0
C 3.313 -1.206 2.132 11 3 195 196 0
C 2.701 -2.266 1.421 11 170 193 194 0
C 3.313 -1.206 3.553 11 194 5 197 0
C 2.701 -2.266 4.263 11 172 196 199 0
C 3.313 -1.206 6.395 11 7 199 200 0
C 2.701 -2.266 5.684 11 174 197 198 0
C 3.313 -1.206 7.816 11 198 9 201 0
C 2.701 -2.266 8.526 11 176 200 203 0
C 3.313 -1.206 10.658 11 11 203 204 0
C 2.701 -2.266 9.947 11 201 178 202 0
C 3.313 -1.206 12.079 11 202 13 205 0
C 2.701 -2.266 12.789 11 180 204 207 0
C 3.313 -1.206 14.921 11 15 207 208 0
C 2.701 -2.266 14.210 11 182 205 206 0
C 3.313 -1.206 16.342 11 206 17 209 0
C 2.701 -2.266 17.052 11 184 208 211 0
C 3.313 -1.206 19.184 11 19 211 212 0
C 2.701 -2.266 18.473 11 186 209 210 0
C 3.313 -1.206 20.605 11 210 21 213 0
C 2.701 -2.266 21.315 11 188 212 215 0
C 3.313 -1.206 23.447 11 23 215 216 0
C 2.701 -2.266 22.736 11 190 213 214 0
C 3.313 -1.206 24.868 11 214 0 0 0
O 0.002 0.080 10.397 188 218 219 0 0
H 0.442 -0.624 9.908 189 217 0 0 0
H -0.550 0.506 9.731 189 217 0 0 0
O -0.159 -0.163 13.219 188 221 222 0 0
H 0.532 0.461 13.471 189 220 0 0 0
H -0.212 -0.084 12.252 189 220 0 0 0
$end

$opt
FIXED
1 XYZ
2 XYZ
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ENDFIXED
$end

$qm_atoms
217:222
$end
output file:
Nuclear Repulsion Energy = 0.00000000 hartrees
There are 658 alpha and 658 beta electrons
**** Step 1: MM calculation on the entire system ****
OPLSAA force field loaded.
Determining angles, torsions, etc. from user defined input
I would like to ask how to set the parameters, vdw and force constant and other parameters for such a complex system? I didn’t understand the manual, thank you!

#2

You need to set them for all atom types that are contained in your $molecule but not loaded by the force field, using the $force_field_params section as speciified here: Q-Chem 4.3 User’s Manual : Stand-Alone QM/MM calculations

#3

I have read the introduction, but there are many atoms that needs to specify. I don’t konw to define how many bond length and angle, or other parameters.In other words, are there any simple ways to determine them?

#4

No. While there are some computational tools for automated force-field parameter generation, they are not part of Q-Chem. I suggest if possible that you try to use an existing force field such as OPLS, CHARMM, AMBER, etc., which can be put into a format that is readable by Q-Chem.

#5

Thank you for your help. However, there are still the problem when we use OPLSAA. The partitial output file as follows:
imptor test 0: 5-5-5-5
imptor test 0: 5-5-5-5
imptor test 0: 5-5-5-5
imptor test 0: 5-5-5-5
imptor test 0: 5-5-5-5
imptor test 0: 5-5-5-5
imptor test 0: 5-5-5-5
imptor test 0: 5-5-5-5
imptor test 0: 5-5-5-5
imptor test 0: 5-5-5-5
imptor test 0: 5-5-5-5
imptor test 0: 5-5-5-5
imptor test 0: 5-5-5-5
imptor test 0: 5-6-5-6
imptor test 0: 5-6-5-6
imptor test 0: 6-5-5-6
imptor test 0: 6-6-5-5
imptor test 0: 6-5-5-6
imptor test 0: 6-6-5-5
Determining VDW/Coulomb pairs… (useList = 0)

Time req’d to get MM system information: 0.0 s (CPU) 0.0 s (wall)
Unknown angle bending parameter for 6-5-6
Unknown angle bending parameter for 6-5-6
Unknown angle bending parameter for 6-5-6
Unknown angle bending parameter for 6-5-6
I don’t konw how to determine them.

#6

In addition, I don’t determine whether is beacause of too large MM systems.

#7

If the force field doesn’t recognize the parameters for the atom types that you have specified, then you need to pick a different force field, or else specify those parameters yourself.