CASSCF optimization file read error; PES scans

Questions
#1

Hi,

PES scan with CASSCF fails because of a gradient file read issue. I see a similar issue was there with optimizations and it is fixed only for optimization jobs. I tried using “GEOM_OPT_DRIVER = OPTIMIZE” but this does not work with either Q-Chem 6.2.1 or 6.2.2.

Is there a work around this issue?

Thank you.

#2

Might be a bug but it’s difficult to diagnose without a full input file. Please use the formatted text button, </> .

#3

Ok, Here is the input

$molecule
+1 1
1        0.000000000      0.000000000     -1.040099538
1        0.000000000      0.000000000     -0.336479538
1        0.000000000      0.000000000      2.099720462
$end
$rem
basis cc-pVTZ
exchange hf
point_group_symmetry false
integral_symmetry false
jobtype pes_scan
scf_print 1
scf_algorithm DIIS_GDM
SCF_GUESS                  SAD
MAX_SCF_CYCLES             250
CAS_METHOD                 2     
CAS_M_S                    0     
CAS_N_ELEC                 2     
CAS_N_ORB                  3     
CAS_N_ROOTS                1     
CAS_SOLVER		   0     
$end
$scan
stre 1 2 0.70362 2.40362 0.1
stre 2 3 2.4362 0.70362 -0.1
$end
#4

Maybe all you need is to include the “FROZEN_SCAN = true” setting in your REM. The only other degree of freedom is the H-H-H angle, which will be relaxed otherwise. Anyway, we can reproduce the error and it does seem like a bug.

#5

Ok, thank you very much. Frozen scan should allow me to continue.

Update,
Using frozen scan allowed the scan to continue without using optimizations.