All Questions
Tagged with orca geometry-optimization
10 questions
3
votes
1
answer
367
views
UseSym Keyword in ORCA fails to find appropriate number of SALCs
I am trying to run some geometry optimizations in ORCA 5.0.4 and I am using the UseSym keyword to ensure that my molecules retain Cs Symmetry during optimization. ...
- 521
5
votes
1
answer
527
views
ORCA crashes because of RI approximation?
I am doing a geometry optimization for a cationic imidazolate-zinc complex.
I'm trying to run an optimization using this input file. It uses the RI approximation.
ORCA seems to be running fine until ...
- 521
4
votes
0
answers
94
views
How to compute only part of molecular Hessian accurately (hybrid Hessian or partial Hessian calculation)?
Hessian is required for minimisation and transition state (TS) optimisation algorithms. While the full Hessian at a certain level of theory is calculated usually for TS optimisation, usually ...
- 7,171
2
votes
0
answers
105
views
How to handle explicit solvent molecules when calculating energies of reactant molecules in isolation [closed]
When determining the energy barrier, it is recommended to compute the energies of reactant molecules in isolation to account for the entropy change of forming the reactant complex (hence factoring ...
- 131
3
votes
1
answer
1k
views
ORCA: Getting the error "mpirun noticed that process rank 0 with PID 383161 on node exited on signal 11 (Segmentation fault)."
I am getting a segmentation fault error when running the following input file below. The calculation runs fine in gas phase and CPCM modes, but fails with SMD. What could be the issue? Some are saying ...
- 131
4
votes
1
answer
287
views
How does ORCA treat intermediates in Nudged Elastic Band (NEB) calculations
I'm trying to run a quite complicated NEB optimization with (hopefully) one intermediate structure.
But before losing time, I was wondering:
how does ORCA treat that intermediate?
does ORCA optimize ...
- 1,009
7
votes
1
answer
1k
views
What are the output files generated by an NEB calculation?
I just used Orca for the first time.
Can someone address me a valid guide to understand all the files in the directory?
I'd like to perform a Nudged Elastic Band (NEB) calculation, but I'm stuck ...
- 1,009
11
votes
1
answer
275
views
Using "soft" constraints / bias in geometry optimization?
I study molecules weakly bound to nanoclusters and surfaces.
During geometry optimization, I often run into problems like for example a small metal cluster behave nicely and has a given, stable ...
- 1,819
27
votes
2
answers
3k
views
Is it right to neglect very small imaginary frequencies?
I'm running a DFT optimization (B3LYP/def2-TZVP) and frequencies in ORCA for a molecule. And I get one or two very small (1-6 cm^-1) imaginary frequencies which corresponds to a slight bend of the ...
- 2,383
11
votes
2
answers
1k
views
Analytic gradient for DLPNO-CCSD
Is there a formula for analytical gradients (for geometry optimization) for the DLPNO-CCSD method? I ask because I know that it is not implemented in ORCA. Maybe PNO-CCSD is implemented in MRCC or ...
- 3,983