Questions tagged [symmetry]
Questions relating to symmetries and symmetry groups encountered in materials modeling.
14
questions
9
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1answer
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Partial density of states in random solid solutions
This question comes as a follow-up to https://mattermodeling.stackexchange.com/a/2214/116; nonetheless, it is relevant on its own as well.
To designate a particular crystal structure to a random ...
8
votes
1answer
66 views
Why does mcsqs change the space group of generated SQS?
I made a binary special quasi-random structure (SQS) using mcsqs (distributed as part of the ...
4
votes
0answers
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How to classify ionic and covalent excited-states?
In spectroscopy it is common to describe excited-states as ionic or covalent.
I understand the concept on a toy model e.g. $\ce{H2}$ with a minimal basis set
$$
\Phi_0 = [\chi_A(1) + \chi_B(1)][\...
11
votes
2answers
190 views
Effect of ISYM tag on Partial Density of States (VASP version < 6)
This is from the entry for LORBIT in the VASP Wiki.
For LORBIT >= 11 and ...
7
votes
1answer
99 views
Inversion symmetry in 2D materials
Transition metal dichalcogenides (TMDs) are composed of three atomic planes and often two atomic species: a metal and two chalcogens. The honeycomb, hexagonal lattice has three fold symmetry and can ...
9
votes
1answer
157 views
Get fractional coordinates from special Wyckoff positions
I'm trying to get the fractional coordinates for Mo and S, for MoS$_2$-2H, where 2H means the phase. MoS$_2$-2H is a bilayer, in which each layer is separated from each other by Van der Waals forces. ...
8
votes
0answers
30 views
Symmetry of glide planes
I am trying to understand the symmetry elements of space group number 194 (P$6_3$/mmc), which is hexagonal and has 24 symmetry operations.
In the table of symmetry operations it says that it has three ...
14
votes
4answers
261 views
How is group theory used to deduce which of these integrals are equal to 0?
The number of all two-electron integrals:
$$
\tag{1}
\langle \phi_1 \phi_2|\phi_3\phi_4 \rangle = \int d^3\mathbf r' \int d^3\mathbf r'' \, \phi_1(\mathbf r'') \, \phi_2(\mathbf r') \frac{1}{|\mathbf ...
15
votes
2answers
446 views
How to deduce phase transitions from a phonon calculation?
I came across the concept of using phonons to establish a material's dynamical stability, based on whether or not imaginary frequencies are present in its phonon band structure.
What I am struggling ...
13
votes
1answer
727 views
How to understand time reversal symmetry in graphene
A lot of references say that the Dirac cone in graphene is protected by inversion and time reversal symmetries. How can one understand this statement? How can one show explicitly that the gapless ...
11
votes
1answer
110 views
Dealing with symmetry of ordered primitive cell during DFT structure relaxation
I have a large disordered cubic structure that I would like to do AIMD on to look at cation diffusion. I found the primitive cell and then ordered it to create several configurations. I will then ...
18
votes
1answer
961 views
Is the number of possible Bravais lattices a mathematical fact?
Almost anyone that has taken a Solid State Physics course will know, that any 3D crystal must be in one of the 14 Bravais lattices due to symmetry operations and space filling.
In 2015, a paper was ...
14
votes
1answer
121 views
conceptual problem about the energy band along the High symmetry point in the Brillouin zone
When we calculate the band structure of certain material, we only have to calculate the value along the high symmetry point which enclose the Irreducible Brillouin Zone. Why the information lie in the ...
9
votes
1answer
94 views
What is the difference between U(1) and O(2) symmetry?
To my understanding, they both refer to circular symmetry. I know U(1) is the complex plane, and I think O(2) is real numbers. I have seen them used more or less interchangably, but is there actually ...
