Questions tagged [orca]
For questions about (or involving) the ORCA electronic-structure package.
91 questions
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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 ...
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3
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What is the largest system that has been studied by the coupled cluster method?
This is parallel to the analogous question about the largest DFT calculation: What is the largest material that has been studied using density functional theory?
I assume we allow high performance ...
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12
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3
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701
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Quantum chemistry in external electrostatic field?
Which quantum chemistry methods can be used in an external electrostatic field? Also which software supports that? I'm interested in anything from semiempirical (eg XTB) to DFT (eg ωB97, B3LYP-D3) ...
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How do you calculate the change in dipole moment from ground to first excited state using ORCA?
How do you calculate the change in dipole moment from the ground to first excited state using ORCA? I have done DFT to get the dipole moment at the ground state and TDDFT of this neutral molecule. How ...
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11
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2
answers
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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 ...
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11
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2
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467
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How to calculate DFT energy with density from another level of theory?
I need to calculate the DFT energy given the density of another level of theory, for example Hartree Fock.
$E[\rho_{HF}]$
This is sometimes used to fix various electron delocalization errors in ...
- 8,025
11
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2
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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 ...
- 7,171
11
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1
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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 ...
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11
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0
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I ran TDDFT on some small molecules. For some files, the ORCA output files cut short and contain no absorption data. What could be the reason? [closed]
Below is just the end of the output file, and the top of the input file. This is for the molecule FDICTF. The calculation did not run out of time. I ran a batch of 15 molecules, all with same ...
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10
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1
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How to swap orbitals in ORCA?
I am trying to swap orbitals for a high-spin iron(IV) complex. The orbitals that correspond to the iron are not in any of the SOMOs.
I am using the pDynamo QM/MM program, which is an interface for ...
- 1,546
10
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1
answer
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Constraining a set of atoms in the MM region using pDynamo (CHARMM/ORCA interface)
I am trying to perform a QM/MM optimization in which my substrate is in the MM region. However when this happens there are significant changes to the geometry (undesired). I want to avoid fixing all ...
- 1,546
9
votes
2
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2k
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Different types of transition dipole moment in ORCA output
In the ORCA output for a TD-DFT calculation, there are two types of spectra printed. One is called "transition electric dipole moment" and "transition velocty dipole moment".
...
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9
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1
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ORCA 6 slower than ORCA 5?
Has anyone else noticed that ORCA 6 is behaving slower than ORCA 5? For example, if I run the simple test job:
...
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9
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1
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QuasiRRHO in Orca
I read that ORCA runs a QuasiRRHO calculation based on Grimme approximation, at the end of a freq calculation.
Unfortunately, I wasn't able to find the default value for the CutOffFreq. In Grimme's ...
- 1,009
8
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1
answer
677
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Why is my ORCA calculation of nitrogen iodide failing?
I am using ORCA version 4.2.1 to calculate on the RI-BP86/def2-SVP level of theory the molecule $\ce{NI3}$. I would assume this to be a rather trivial matter, but I am running into an error. I've only ...
- 1,591
8
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3
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410
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Different results from MP2 calculations on same geometry in ORCA
I am trying to do a segmented potential energy scan around a dihedral for a molecule. I have optimized the geometry to a minima, and the scan runs from [-180, 180] in steps of two points at a time.
...
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8
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1
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How to get the .47 file from ORCA for natural bonding orbital analysis
I am trying to perform NBO analysis with relaxed density matrix with the open-source program JANPA. I am following the guide here. The first step is to get the NBO input .47 file from Orca v4.2.1. The ...
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8
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1
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129
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What would be the best tool to simulate FTIR spectra of molecules?
I tried to simulate a spectrum of a porphyrin using the orca 5.0.4 program, calculating the frequencies and simulating the spectrum with the orca_mapspc program from the orca package, however the ...
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7
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3
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3k
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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 ...
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7
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1
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317
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Simulating autoionization of small molecules using DFT or AIMD
From what I'm reading, simulation of auto-ionization in liquid substances is hard to do using gas phase DFT or AIMD [1][2][3]. I am using ORCA to do my work and I must confess that I'm shocked to see ...
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7
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1
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184
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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 ...
7
votes
1
answer
1k
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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
7
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1
answer
967
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Numerical Frequency Parallelization in ORCA
In orca it is possible to use NumFreq and AnFreq to get the numerical and analytical frequencies, but the analytical frequencies take a large amount of memory and computing time compared to numerical ...
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7
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1
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How can I calculate the energy gap between the singlet and triplet state using ORCA?
I came across this publication that calculates the $S_1$ - $T_1$ energy gap using TDDFT as implemented in Gaussian. I would like to do the same using ORCA. Im extremely new to ORCA and local orbital ...
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7
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1
answer
974
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Adding external electric field in ORCA with specific strength
Can anybody share methods to apply an external Electric field in ORCA? thanks!
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1
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For software that does not support FCIDUMP format, what format is used and how can we get the software to interact with FCIDUMP integrals?
Complementary to this question: How do the various programs read or write integrals in FCIDUMP format? which attempts to list all electronic structure packages that support the ...
7
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1
answer
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How to properly define %maxcore in ORCA
The %maxcore parameter in ORCA gives the memory per core needed for a calculation, however it is unclear to me if this should be the entire memory available to the ...
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7
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1
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319
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Do ORCA input files allow for multi-line comments or different comment syntaxes?
I have a self-inflicted problem with the input files that I am generating using RDKit in order to automate my ORCA jobs. I like to keep track of data such as:
The ...
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7
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1
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How to localize orbitals in pDynamo (CHARMM/ORCA interface)?
Does anyone know how to localize orbitals in pDynamo (CHARMM/ORCA interface). I am trying to identify the correct orbitals to swap for my high-spin iron(IV) system.
- 1,546
6
votes
2
answers
754
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Bromine basis set problem
I'm trying to compute the energy of the benzyl bromide with orca. I need it to be at ωB97x-d4/6-31g(d) level. Orca throws me the following error.
...
- 1,009
6
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1
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926
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Running multinode parallel Orca calculation without a work load manager (scheduler)
I wonder, if someone has run (runs) parallel Orca calculations on at least two nodes without a work load manager (scheduler)? I am asking because I have several interconnected servers (nodes) I'd like ...
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1
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255
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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 ...
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6
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1
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131
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Mathematical model/open source code to obtain displaced geometries along a normal mode from vibrational frequency calculation
I am looking for a mathematical model which will produce the displacement vectors from vibrational frequency calculations. I use ORCA for the calculation of the frequencies and generally use Chemcraft ...
6
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1
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264
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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 ...
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6
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1
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894
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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:
...
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6
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0
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935
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MOLDEN file from ORCA output [closed]
I'm trying to convert an ORCA output file into MOLDEN file (via molden itself).
I hit the "Write" button and it converts the file, yes, but the displacement vector s are zeros. I need that ...
- 1,009
6
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0
answers
760
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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 ...
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5
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2
answers
812
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5
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2
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166
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Reintegrate calculation results from ORCA using finer grid?
I have made a bunch of calculations in ORCA to compare them to results from this paper. The original calculations from this paper were done in TurboMole. I tried to recreate the method as best I could ...
- 521
5
votes
2
answers
374
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Trying to get concurrent results for a TDDFT calculation in Gaussian and ORCA
I am trying to do a simple TDDFT calculation in both Gaussian and ORCA from the exact same reference Geometry. I am using the same functional (making sure to use ...
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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?
...
- 1,009
5
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1
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Modify ORCA orbitals for CASSCF
I have run a HF calculation on naphthalene and I have checked the MOs that have been obtained. Now, I have to select my active and inactive orbitals for CASCF(10,10). As there are 34 occupied orbitals,...
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5
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1
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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:
...
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5
votes
2
answers
322
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OpenMPI not running under SLURM in UBUNTU with ORCA?
I have ORCA 5.0.4, OpenMPI 4.1.1 and SLURM in UBUNTU 22 in a single PC with 16 threads.
I have setup this pc and, when I run orca alone, openmpi works. But, when I submit orca through slurm, the ...
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1
answer
2k
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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
5
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1
answer
1k
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Unrecognized or duplicated keyword error using ORCA
I wanted to run ORCA 5.0.2 with the following input:
...
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5
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1
answer
277
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Does it make any sense to run a TD-DFT calculation with Finite-Temperature SCF active?
I recently received the task to investigate what is happening in a fluorescent molecule in different temperatures. How the electronic population is changing and how is this affecting the electronic ...
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5
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1
answer
425
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ORCA: CIS calculation for Helium atom
I want to understand ORCA output for CIS calculations.
From the input file
...
- 357
5
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1
answer
451
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Non-equilibrium CPCM for Orca Absorption Spectra
I run into this article[1] in which they figure out that if you want to correctly simulate electronic spectra you have to consider the non-equilibrium solvation.
I've made research into the ...
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5
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1
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527
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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