Using Mixture of Basis Set and Pseudo-Potentials

Optimization of BBr3: This compound contains both of the light and heavy atom which indicates using just only either basis set o pseudo-potential does not computationally efficient to calculate this kind of molecule.

The important keyword for using ECP basis set:

  • $Functional/GEN pseudo=read gfinput

The general format of specified basis set at the end of input file is the following

charge spin.mult
coordinates
...
...
... 
                                       (blank line) 
atomic symbols (space) 0 (zero) 
normal basis set 
****                                   (four stars) 
atomic symbols (space) 0 (zero) 
pseudo-potential basis set 
****                                   (four stars) 
                                       (blank line) 
atomic symbols (space) 0 (zero) 
pseudo-potential 
                                       (blank line)
                                       (blank line)

Example of Gaussian file of BBr3 optimization for ECP calculation 

%chk=TH_BBr3_OPT_GEN.chk
# opt b3lyp/gen geom=connectivity pseudo=read gfinput
integral=grid=ultrafine

BH3 OPTIMIZATION

0 1
 B                  0.00000000    0.00000000    0.00000000
 Br                -1.74937106   -1.01000043    0.00000000
 Br                 0.00000000    2.02000000    0.00000000
 Br                 1.74937106   -1.01000043    0.00000000

 1 2 1.0 3 1.0 4 1.0
 2
 3
 4

B 0
6-31G(d,p)
****
Br 0
LanL2DZ
****

Br 0
LanL2DZ



Summary

Filename = TH_BBr3_OPT_GEN.log
BH3 OPTIMIZATION
File Name = TH_BBr3_OPT_GEN
File Type = .log
Calculation Type = FOPT
Calculation Method = RB3LYP
Basis Set = Gen
Charge = 0
Spin = Singlet
E(RB3LYP) = -64.43644947 a.u.
RMS Gradient Norm = 0.00000384 a.u.
Imaginary Freq = 
Dipole Moment = 0.0000 Debye
Point Group = D3H
Job cpu time:  0 days  0 hours  0 minutes 30.0 seconds.

Structural parameter

The bond distance of B-Br is 1.93396 A
The bond angle of Br-B-Br is 120 degree