Questions tagged [geometry-optimization]
The geometry-optimization tag has no usage guidance.
10
questions
5
votes
1answer
129 views
When should “vc-relax” be performed over “relax” calculations in Quantum ESPRESSO?
I'm new to Quantum ESPRESSO and I have read that there are several scenarios when relax calculations are preferred over vc-relax calculations, for example in maintaining vacuum while modelling surface....
10
votes
2answers
167 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 ...
13
votes
5answers
2k views
Can I use two different codes?
Can I use one code for geometry optimization and another code for a single point calculation on that optimized geometry? Can one publish results like that?
9
votes
2answers
112 views
Geometry optimization for n-layers in VASP
What is the best way to optimize monolayer geometry in VASP?
Should the same method be used for an n-layer (n=2,3,4,5)?
11
votes
2answers
134 views
Permissible amount of forces on ions in a relaxed structure
An equilibrium structure would be at a local minimum but that doesn't happen with all relaxation calculations. Relaxed structures tend to have some resultant forces on ions. What amount of these ...
11
votes
1answer
170 views
How would you report the lattice parameters of an alloy, modelled using a supercell
There is a whole lot of literature behind ab initio modelling of alloys with statistical site occupancies. These include VCA, SQS, CPA, supercell approach, etc. This question does not aim to compare ...
17
votes
2answers
908 views
Logic of published geometry optimization results without checking phonons
I see that in many papers where optimization results presented, they do not mention phonons and their force convergence criterion is 0.01 eV/A. Can you publish a result like that? And is not this ...
7
votes
0answers
71 views
How do I predict the structure of a nanoparticle with Calypso and Quantum ESPRESSO?
I want to create a nanoparticle of CuO and predict it's structure. I've done unit cell relaxation with Quantum ESPRESSO. One tool to predict nanocluster structure is Calypso which is PSO-based. I'm ...
14
votes
3answers
103 views
Candidate structures for global minimum determination
What are the best packages that can generate candidate structures for quantum chemical optimization (DFT or CCSD) to find the global minimum? I am working on the gas-phase small inorganic clusters (...
8
votes
2answers
255 views
Is there a possibility to change the initial crystal system during full geometric relaxation?
One of the challenges of modelling completely new material using DFT is the selection of initial geometry. Usually, an experimental structure (cif) which appears to be similar to the new material in ...
