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ORCA4

TiO2 clusters

Input

Geometry file

System Charge Multiplicity
neutral molecule 0 1
protonated PAHs C16H15+ 1 1
cation H2O+ 1 2
radical cation PAHs C16H14+ 1 2
- Linear molecules have to align with z-axis for vibrational analysis

spin multiplicity

$$\text{multiplicity} = \text{number of } \alpha \text{ electrons} - \text{number of } \beta \text{ electrons} + 1$$ - When #electrons is odd, then multiplicity must be even (2, 4, 6, ...). - When #electrons is even, then multiplicity must be old (1, 3, 5, ...).

RI

RIJCOSX

XC

meta-GGA

libxc

Using MN15 functional in ORCA 4.2.1 from libxc

! RIJCOSX def2-TZVP def2/J Opt nopop 
%scf maxiter 600 end 
%method
method dft 
exchange hyb_mgga_x_mn15 
correlation mgga_c_mn15 
end
%maxcore 1000 
%pal nprocs 16 end 
*xyz 0 1 
C -0.047131 0.664389 0.0
O -0.047131 -0.758551 0.0
H -1.092995 0.969785 0.0
H 0.878534 -1.048458 0.0
H 0.437145 1.080376 0.891772
H 0.437145 1.080376 -0.891772
*

Broken symmetry

CASSCF

Complete Active Space Self-Consistent Field (CASSCF) - CASSCF(N,M): N-electrons are active in M orbitals.

%casscf nel N
        norb M
        end

Metadynamics

ORCA 5.0.0 and 5.0.1 has a bug in interpreting the second Colvar. This can be solved by adding 3 more zeros in the end.

  Metadynamics Colvar 1 Scale 1.0_A Wall Lower 0.0 50.0 Upper 10.0 50.0 Range 0.0 10.0 100
  Metadynamics Colvar 2 Scale 1.0_A Wall Lower 0.0 50.0 Upper 10.0 50.0 Range 0.0 10.0 100 0 0 0

Alternatively, putting two Colvars in the same line also solves this bug

  Metadynamics Colvar 1 Scale 1.0_A Wall Lower 0.0 50.0 Upper 10.0 50.0 Colvar 2 Scale 1.0_A Wall Lower 0.0 50.0 Upper 10.0 50.0 Range 0.0 10.0 100 0.0 10.0 100

Tips

Parallel run on multiple nodes

One has to create JOBNAME.nodes in the running directory to run on multiple nodes. echo $SLURM_NODELIST >> JOBNAME.nodes will create s31n[07-09] which cannot be recognized by ORCA. The following script gives the correct multiple nodes setting.

#SBATCH --nodelist=s31n[07-09]
#SBATCH --ntasks=36
#SBATCH --ntasks-per-node=12
#SBATCH --cpus-per-task=1

# change directory to the local scratch-directory, and run:
cd /scratch/$SLURM_JOB_ID
cat > orca.nodes <<!
s31n07 slots=12
s31n08 slots=12
s31n09 slots=12
!

Warnings

WARNING: For RIJCOSX frequencies GRIDX4 or larger grids are recommended

Errors

spin

[file orca_main/mainfcts.cpp, line 625]: Error : multiplicity (2) is even and number of electrons (204) is even -> impossible

Geometry

----------------------------------------------------------------------------
                               ERROR !!!
   The optimization did not converge but reached the maximum 
   number of optimization cycles.
   As a subsequent Frequencies calculation has been requested
   ORCA will abort at this point of the run.
   Please restart the calculation with the lowest energy geometry and/or
   a larger maxiter for the geometry optimization.
----------------------------------------------------------------------------
  [file orca_main/run.cpp, line 10680]: ORCA finished with error return - aborting the run