All Questions
Tagged with orca computational-chemistry
17 questions
4
votes
0
answers
30
views
How to plot orbitals for S1->T1 transition in Orca
I use TD-DFT and want to examine how molecular orbital changes upon ISC from S1 to Tx state and refer to confirm El Sayed rule. How to achieve it if NTO are not generated for S1->Tx transitions? If ...
- 563
1
vote
1
answer
179
views
Problematic optimization of excited states
I work with Orca 5.0.4 (without access to version 6.0) on a symmetric metal-centered system. I'm currently running excited state optimizations, and while S1-S3 and T1, T2, and T4 have optimized ...
- 563
3
votes
1
answer
80
views
Mixing functionals in TD-DFT opt
I work with copper complexes containing at least 100 atoms (including a single Cu, nitrogens, carbons, and hydrogens). According to Grimme's paper, the benchmark level for geometry optimization is ...
- 563
5
votes
1
answer
88
views
Do oscillator strengths matter when matching theoretical and experimental outcomes?
I use ORCA to do TD-DFT studies. The experimental maximum absorption is esteemed to 445.0nm . Benchmark computations were conducted and this is the exemplatory (part of) the output:
...
- 563
6
votes
1
answer
255
views
Assessing excited state lifetime with TD-DFT
My question is brief — is it possible to estimate excited state lifetimes using computational chemistry (DFT/TD-DFT) tools? I am aware this may be a rough approximation (e.g., neglecting non-radiative ...
- 563
3
votes
1
answer
132
views
Cannot reproduce excitation energies in Orca
I do TD-DFT studies in Orca 5.0.3 on porphyrin system and hence at the very beginning I need to pick functional that reproduce excitation energies.
The experimental reported values equal: 691, 656, ...
- 51
4
votes
1
answer
201
views
Question on CPU timings and/or ratio resp. DLPNO-CCSD(T) and wB97X-2-D for protein of ca. 1M Da
Suppose one has a protein of about 1 million Da, and performs a DLPNO-CCSD(T)/def2-TZVPPD/AutoAux/AutoAux calculation, and then performs a wB97X-2-D/def2-TZVPPD/AutoAux/AutoAux calculation, both via ...
- 870
7
votes
3
answers
3k
views
Running an ORCA calculation from Python
I'm a master's student and recently I started doing computational chemistry calculations using ORCA program.
This program works by command line and I saw that the majority of computational chemistry ...
- 165
5
votes
3
answers
753
views
Energy of each fragment in ORCA?
After the definition of the fragments in the geometry section of the calculation, is there a method to call, or a keyword to turn on, in order to obtain the energy of the fragments themselves?
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- 1,009
5
votes
1
answer
2k
views
Numerical Evaluation of Hessian?
I am trying to understand the construction of Hessian matrix using numerical differentiation (NUMFREQ option in ORCA for example). I understand that Hessian is a square matrix containing second ...
- 4,066
6
votes
1
answer
264
views
Is it possible to restrict the calculation of frequencies in ORCA program?
I looked in the orca manual but didn't find anything, but in the case of having a molecule adsorbed in a cluster, is it possible to perform the frequency calculation only on the molecule and not on ...
- 365
6
votes
1
answer
894
views
Unrecognized or duplicated keyword error using ORCA DFT calculations using avogadro
I'm using Avogadro to generate an input for ORCA, however, when I'm trying to run that input in ORCA it says:
...
- 61
4
votes
0
answers
3k
views
ORCA finished by error termination in SCF gradient [closed]
I try to optimize and compute frequencies for the system built up from C, O, H, and Co atoms in the following functionals: B2PLYP, B2PLYP-D3, B3LYP, B3LYP-D3, BLYP, BLYP-D3, DSD-PBEP86, PBE, PBE-D3, ...
- 51
7
votes
1
answer
184
views
Is It possible to do microkinetic modelling for liquid phase reactions, in the presence of a catalyst?
As from the title, I want to do NEB-TS for chemical reactions in the liquid phase, and use the information to calculate reaction rates/kinetic rates.
I know that the NEB-TS is possible in the liquid ...
5
votes
1
answer
1k
views
Unrecognized or duplicated keyword error using ORCA
I wanted to run ORCA 5.0.2 with the following input:
...
- 343
6
votes
0
answers
760
views
How do you perform parallelization of NEB-TS in ORCA? [closed]
I have tried running a NEB-TS calculation in orca with %pal nprocs 32, but I get an error saying ...
- 61
11
votes
2
answers
2k
views
What are Pair Natural Orbitals?
Recently, I came across electron correlation methods that use local pair natural orbitals (LPNOs) or domain-based local pair natural orbitals (DLPNO), such as DLPNO-MP2, DLPNO-CCSD etc. The dynamic ...
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