PES Scans with PC GAMESS/Firefly: Example
For relaxed scans, you should use the RUNTYP=rsurface, and use ifreez in $statpt and PC GAMESS/Firefly-specific extensions in the $surf group. You have to perform scan using internal coordinates. Below is the sample for CH3-CH3 molecule.
$CONTRL RUNTYP=rsurface NZVAR=18 COORD=ZMT mplevl=2 $END
$SYSTEM TIMLIM=500 MEMORY=30000000 $END
$BASIS GBASIS=tzv ndfunc=1 $END
! To freeze coord # 12 during constrained optimization
$statpt opttol=1d-5 nstep=1000 IFREEZ(1)=12 $end
! To scan along coord # 12
$surf ndisp1=33 disp1=3.75 vect1(12)=1 orig1=0 $end
$DATA
CH3-CH3
C1
C
C 1 r1
h 1 r2 2 a1
h 1 r2 2 a1 3 d1
h 1 r2 2 a1 3 d2
h 2 r2 1 a1 4 dx
h 2 r2 1 a1 6 d1
h 2 r2 1 a1 6 d2
r1=1.54
r2=1.09
a1=109
d1=120
d2=-120
dx=0
$END
$ZMAT IZMAT(1)=
1, 2, 1,
1, 3, 1,
2, 3, 1, 2,
1, 4, 1,
2, 4, 1, 2,
3, 4, 1, 2, 3,
1, 5, 1,
2, 5, 1, 2,
3, 5, 1, 2, 3,
1, 6, 2,
2, 6, 2, 1,
3, 6, 2, 1, 4,
1, 7, 2,
2, 7, 2, 1,
3, 7, 2, 1, 6,
1, 8, 2,
2, 8, 2, 1,
3, 8, 2, 1, 6,
$END
At the end of the output, you'll find the tables with relaxed PES curve.
ENERGY DELTA MAP(S) (W.R. TO THE LOWEST FOUND)
------------------------------------
ICOORD1, | ENERGY
COORD1 | DELTA
---------------+--------------------
1 ( 0.00000)| 0.0048607787
2 ( 3.75000)| 0.0048076271
3 ( 7.50000)| 0.0046512997
4 ( 11.25000)| 0.0044006116
5 ( 15.00000)| 0.0040690494
6 ( 18.75000)| 0.0036733200
7 ( 22.50000)| 0.0032319901
8 ( 26.25000)| 0.0027642359
9 ( 30.00000)| 0.0022889516
10 ( 33.75000)| 0.0018240699
11 ( 37.50000)| 0.0013860863
12 ( 41.25000)| 0.0009897255
13 ( 45.00000)| 0.0006477219
14 ( 48.75000)| 0.0003706143
15 ( 52.50000)| 0.0001667135
16 ( 56.25000)| 0.0000419571
17 ( 60.00000)| 0.0000000000
18 ( 63.75000)| 0.0000419492
19 ( 67.50000)| 0.0001667268
20 ( 71.25000)| 0.0003706748
21 ( 75.00000)| 0.0006479067
22 ( 78.75000)| 0.0009901676
23 ( 82.50000)| 0.0013869550
24 ( 86.25000)| 0.0018255374
25 ( 90.00000)| 0.0022911254
26 ( 93.75000)| 0.0027670879
27 ( 97.50000)| 0.0032353052
28 ( 101.25000)| 0.0036767116
29 ( 105.00000)| 0.0040720127
30 ( 108.75000)| 0.0044027392
31 ( 112.50000)| 0.0046524219
32 ( 116.25000)| 0.0048079360
33 ( 120.00000)| 0.0048607787