Unanswered Questions

124 questions with no upvoted or accepted answers
17
votes
0answers
166 views

What are the tools available for point defects calculations?

As far as I know, there are mainly PyCDT, PyDEF, pylada and some part of pymatgen. As a new user to those tools, which one would be a good choice? It would be appreciated if you could explain one of ...
16
votes
0answers
100 views

What are the recent developments of TDDFT to simulate the excited properties of materials?

The time-dependent density functional theory (TDDFT) and the many-body perturbation method (GW@BSE) are considered as the two most popular and successful methods to describe the excited-stated ...
15
votes
0answers
111 views

How to find the projected Hamiltonian for lowest flat-band in general?

In [1], starting with the bosonic Hamiltonian (Eqn. 1) for the dice lattice model with half flux density (with Ahronov-Bohm phases incorporated), \begin{equation} H=-t\sum_{\langle j,\mu\rangle}(a^\...
13
votes
0answers
115 views

Empirically determining thermostat damping factor

Is there a way to determine an appropriate thermostat damping factor given a timestep size and a numerical integration method? I am computing a set of simulations in LAMMPS, using ReaxFF, tracking ...
13
votes
0answers
154 views

Why does the Wolff algorithm slow down in a 4-body Ising model?

In the paper that introduced "Self-learning MC" (an ML-inspired MC technique, as I understand) the authors consider a many-body Ising model as an example to show the efficiency of their ...
12
votes
0answers
81 views

What are the recent developments of GW@BSE to simulate the excited properties of materials?

The time-dependent density functional theory (TDDFT) and the many-body perturbation theory (GW@BSE) methods are considered as the two most popular and successful methods to describe the excited-stated ...
12
votes
0answers
97 views

How do I know if the reconstruction in the picture is a 2 x 2 reconstruction?

How do I know if the reconstruction in the picture is a 2 x 2 reconstruction or not?                                     I believe that this corresponds to a 2x2 reconstruction because there's an even ...
12
votes
0answers
159 views

First order variation of the wave function of conduction states

The first order variation of the wave function $\Delta \psi_n$ is obtained by standard perturbation theory (Eq. 25 of ref 1): \begin{equation} (H_{SCF}-\epsilon_n)|\Delta \psi_n \rangle = -(\Delta V_{...
12
votes
0answers
108 views

Sample LAMMPS file for graphene growth on a metal surface

I am working with graphene growth on metal substrates. But I need some sample files to know if I am doing it in the right way because running multiple simulations in LAMMPS takes a lot of time. Can ...
11
votes
0answers
97 views

CP2K vs BigDFT comparison

I typically run DFT calculations with 1000 to 5000 atoms using CP2K. This works fine but I'm interested in BigDFT also. Is there anyone here that has experience using BigDFT and is able to compare ...
11
votes
0answers
105 views

Inconsistent data of chemical potential from different papers

I am looking for chemical potential from literature.$^{1,2}$ I compared the method and data they provided. They use the Fitted Elemental Reference Energy method via GGA+U on VASP employing PAW. U ...
11
votes
0answers
99 views

Adiabatic equation related to the Berry phase for lambda with first order terms

Consider the following derivation in David Vanderbilt's book "Berry Phases in Electronic Structure Theory - Electric Polarization, Orbital Magnetization and Topological Insulators" (2018, ...
10
votes
0answers
82 views

How does one project out the translations and rotations from a hessian?

I've recently written a simple code to numerically compute the hessian of some function (at a point). Most electronic structure packages will compute the hessian and then project out the translations ...
10
votes
0answers
122 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_{...
10
votes
0answers
43 views

How can one computationally determine the flammability of a molecular system?

I can imagine one aspect of flammability (the ability of a substance to ignite on fire) to include calculating the kinetics and thermodynamics of the reaction of the system with oxygen. This is not ...

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