Unanswered Questions
266 questions with no upvoted or accepted answers
14
votes
0
answers
163
views
Handling multiple self-consistent solutions with DFT+U
It is well-established that within the DFT+U framework, one can achieve several self-consistent solutions with greatly varying energies for the same exact magnetic ordering. In 2010, Meredig et al. ...
14
votes
0
answers
260
views
Orbital magnetization in periodic solids
The orbital magnetization in periodic solids has been nicely described by the so-called modern theory of magnetization [1,2,3,4].
$$\tag{1}
\mathcal{M}_{orb} = -\frac{1}{2} \Im \sum_{n,\mathbf{k}} f_{...
13
votes
0
answers
379
views
Calculating Core-Level Binding Energies (XPS) using DFT
I'm pretty new to DFT calculations but I'm trying to learn how to do X-ray photoelectron spectroscopy (XPS) calculations, particularly for open-shell molecular systems in common non-periodic DFT codes....
9
votes
0
answers
184
views
How to do parity analysis of band extrema?
To check whether electronic transitions are allowed between valence band maximum (VBM) and conduction band minimum (CBM) as per Laporte's rule, the parity of VBM/CBM is needed to be known. This paper ...
- 939
8
votes
0
answers
89
views
How to use the HNC approximation to find the change in grand potential
I am reading Hansen and MacDonald's Theory of Simple Liquids, and I am going through Integral Equation theories.
In section 4.3, they put forward the equation (4.3.14),
$${\small \Omega _{\phi} = \...
- 15.9k
7
votes
0
answers
56
views
Empirical approaches for predicting mass spectra
One way of predicting a mass spectrum of a new molecule is to run a semi-empirical BOMD computation where the molecule is ionized, gets a big energy and starts dissociating. However, I suppose that in ...
- 1,684
7
votes
0
answers
108
views
In DFT codes, which energy is forces derivatives of?
There was a discussion in our research group recently, that I did not follow completely, but the crux was:
In most DFT codes (especially VASP), when we compute the forces, which energy are the forces ...
- 615
7
votes
0
answers
157
views
Correct method for structure optimization using DFT tools
Lets's say I want to start off DFT calculations for a material whose experimental cell constants are known. So I have two ways to get the correct structure to later on calculate, say, band structure ...
- 939
7
votes
0
answers
95
views
Degenerate local-orbital radial functions
I am trying to do a simple groundstate calculation with the exciting code for a perovskite structure with 4d-electron elements. The code uses a muffin-tin approach and expands the wavefunctions inside ...
- 330
7
votes
0
answers
179
views
How do you calculate a full quartic force field for anharmonic frequencies?
I am an experimental chemist interested in anharmonicity—I am particularly interested in how to calculate anharmonic frequencies. The method I have the most experience with is (generalised) second ...
7
votes
0
answers
161
views
Calculation of charge transport with the non-orthogonal basis Hamiltonian based on the non-equilibrium Green's function method
I am thinking about one question. If the Hamiltonian matrix is based on the non-orthogonal basis, how to compute the charge conductance with the Non-Equilibrium Green's Function (NEGF) method.
Suppose ...
7
votes
0
answers
167
views
Scaling and speed-up of real-space DFT calculations using finite elements approach
I have recently encountered this paper in which the authors have formulated Kohn-Sham equations using the finite elements package deal.II, leading to an open-source software called DFT-FE.
It stated ...
6
votes
0
answers
116
views
Spin-orbit coupling(SOC) in geometry optimisation
When I tried including SOC during the optimization of InBi lattice constants, the lattice constant increased from 4.6 Å (without SOC) to more than 6 Å (with SOC), which seems like an 'incorrect' ...
- 65
6
votes
0
answers
71
views
What matter modeling problems could be solved with 100 error-corrected qubits?
IBM, Infleqtion, QuEra, and other quantum hardware companies have announced roadmaps where they expect to have 100 or more error-corrected qubits by the end of the decade. It seems increasingly likely ...
- 6,804
6
votes
0
answers
62
views
Examples of high sensitivity of observable behavior to the choice of DFT functional
Most computational materials science studies perform or reference some sort of baseline process for choosing the DFT functional that they will employ to model their system. It is unlikely that a ...
- 1,658