# Matter Modeling Stack Exchange Community Digest

## Top new questions this week:

### What are the physical consequences of adding a constant to the diagonal of the effective Hamiltonian of monolayer materials?

Effective Hamiltonians modeling many-layered materials are often tuned using some sort of bias voltage. For instance, in a $4\times 4$ Hamiltonian matrix to describe biased bilayer graphene using some ...

density-functional-theory condensed-matter basis-sets model-hamiltonians physical-properties-of-materials

### Are nuclear ab-initio methods related to materials ab-initio methods?

I just read this synopsis in Physics where scientists used first-principles nuclear physics calculations to predict the stability of 700 isotopes up to iron. I didn't know that this was possible, ...

computational-chemistry ab-initio-calculations high-performance-computing computational-frameworks

### How to create a KPOINTS file (k-path) for 4x4x1 supercell bandstructure calculation?

How to generate or create the correct KPOINTS ( K-PATH) file for a 4x4x1 supercell bandstructure calculation ? Is there a software compatible with vasp can do that ?...

density-functional-theory vasp band-structure

### Why does the VASP electronic step not stop after getting converged?

I have just implemented VASP code with Gamma K-point, POSCAR of 128-atom supercell and INCAR like this: ...

vasp numerical-convergence

### How to build a nanocluster?

What are the software tools (if possible open source) or methods we can use for constructing a nanocluster, most preferably with high symmetry such as icosahedron, octahedron, cuboctahedron etc. ?

### What's the relationship between the first HK theorem and the second HK theorem?

The first Hohenberg-Kohn (HK) theorem: The external potential $v(\vec{r})$ is determined, within a trivial additive constant, by the ground-state electron density $\rho(\vec{r})$. From basic quantum ...

density-functional-theory kohn-sham

### How can I know if 3D aperiodic systems are not interacting with each other using Quantum ESPRESSO?

I wanted to observe the Projected Density of States of InP system passivated with Hydride ions. For that, the following input file was created. ...

density-functional-theory quantum-espresso quantum-dots

## Greatest hits from previous weeks:

### How to understand the crystal field splitting of d-orbitals in a trigonal prismatic geometry?

This question is coming from this paper, which investigated the spontaneous spin and valley polarizations of monolayer LaBr2. The geometric information of monolayer LaBr2 is displayed as following (Br:...

solid-state-physics crystal-field perturbation-theory

### Magnetism and Topology

Can magnetism and topological insulating behavior coexist in a material? If yes, can someone refer to a recent work?

magnetism topological-insulators

### What are the types of charge analysis?

I am evaluating the atomic charge of a system using inter-atomic potentials and comparing with using DFT. I know about the following types of partial charge: Mulliken, Bader, Qeq. I wonder what are ...

### Supercomputers around the world

For a matter modelling person, the most valuable resource is computing power. For many of us, computing power at hand limits the scale of problems we can solve. There are many national supercomputing ...

### How to use the ev.x tool in Quantum ESPRESSO?

The requirement I have is to calculate the bulk modulus from the Energy values at certain Volumes obtained via DFT calculations. Can you provide the instructions to use the ev.x tool in the Quantum ...

density-functional-theory quantum-espresso bulk-modulus elasticity curve-fitting

### What are "first principles" calculations?

A newcomer to density functional theory calculations is exposed to jargon which sounds rather non-technical at first. For instance, 'charge density' is something that is actually a term in the ...

density-functional-theory terminology

### Is ARM64 the next big thing?

Considering how GPUs in matter modeling was first recognized in gaming devices like PlayStation, it is also interesting to consider whether ARM64 chips, which are the type of chips in modern smart ...

high-performance-computing software-recommendations soft-question

## Can you answer these questions?

### Calculating the Chern number on a 2D surface of a 3D insulator

I want to calculate the Chern number of a surface of 3D time reversal insulator. I know the 3D topological insulator was characterised by the Z2 index. And the Chern number was used characterised the ...

band-structure topological-insulators tight-binding

### What correlation effect are included in KS-DFT with LDA and GGA?

This post is inspired by this post: What correlation effects are included in DFT? The Kohn-Sham density functional theory (KS-DFT) are considered to be exact and can include all correlation effects in ...

density-functional-theory electron-correlation exchange-correlation