# All Questions

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19 views

### Have Finite Difference Time Domain methods made inroads into dynamical simulation of electron and X-ray scattering by crystals?

I'm afraid this question might be too basic or too naive or both, but here goes! For optical diffraction by periodic nano-structures (gratings, semiconductor manufacturing metrology) the rigorous ...
228 views

### Is there an energy gap correction factor that needs to be used in DFT calculations?

I am a beginner and have performed the DFT calculation in Quantum ESPRESSO for calculation of the direct and indirect bandgap of Silicon. I found the indirect bandgap to be 0.6551 eV. Now, I have ...
17 views

### Is it possible to simulate the Raman spectra via Molecular Dynamics(MD) using the GROMACS package?

I'm new to molecular dynamics and DFT. The aim was to study the Raman spectra of a molecule in a medium. As we know the Raman spectra of a molecule change due to the induced polarization in the ...
248 views

### Si energy band values are not matching with literature values

I have performed the DFT calculation for Silicon in Quantum ESPRESO. I have tried to calculate the electronic band structure, the shape of wiggles of bands are mostly matching but the energy values ...
28 views

### Is there any way to simulate the Polarization vs Electric Field loop of BaTiO3 using Quantum ESPRESSO?

I'm new to the Quantum ESPRESSO package. There are articles outlining the procedure of indirectly simulating the P-E loop of piezo-electric materials via berry phase calculations.One procedure is ...
25 views

### What's the crystal orbital Hamiltonian population?

What's the crystal orbital Hamiltonian population (COHP) or the crystal orbital overlap population (COOP)? What's the relation between the bandstructure or density of states (DOS) and COHP/COOP? Why ...
138 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....
22 views

### How to convert lab frame quaternions and plane normal to misorientation quaternion and crystal plane normal for grain boundaries?

Background Let qA and qB represent unit, orientation quaternions of grain A and grain B of a grain boundary in the lab reference frame, respectively. Let qm be the misorientation quaternion of qA and ...
34 views

### Evaluating $C_v$ for one mole $H_2$ molecules in a quantum simulation

Given an ensemble of $N$ diatomic molecules, we know that the rotational partition function is given by $$Z_r = z_r^N$$ where $$z_r = \sum_{l} (2l+1)e^{-Kl(l+1)}$$ where $K = \beta \hbar ^2 /2I$. I ...
55 views

### How to do spin polarization calculations using Quantum ESPRESSO?

I am currently new to DFT calculations in Quantum ESPRESSO. Though, I have read some research papers for determining spin polarization and Half-metallicity in certain Heusler alloys. These research ...
495 views

### How to know optimal K-points grid values for good DFT calculation?

I am doing DFT calculations with pw.x executable in Quantum Espresso. For this we have to choose right K-points grid in order to perform error-less calculation. But I have no idea about how can I ...
91 views
+50

### Predicting magnetic moment of a metal complex computationally

Recently, for entrance exams, I have been dealing with a lot of weird compounds. One of them is $\ce{K3[Mn(CN)6]}$. The objective was to predict the magnetic moment of the above complex. I predict ...
28 views

### How does MBD (MBD-NL) differ from DFT-TS?

Is anyone familiar with the Tkatchenko's new MBD-NL method? How does it differ from DFT-TS? I couldn't understand everything from the paper.
119 views

### How to choose pseudopotential for DFT calculations in Quantum ESPRESSO?

I am a beginner and newly started running DFT calculations to find out the electronic band structure of certain materials in Quantum ESPRESSO. But we have to select the pseudopotential for running the ...
71 views

### How to build the matter modeling model with appropriate tools?

How to build the matter modeling model with appropriate tools? When we perform matter simulation with first-principles calculation, building a reasonable model always be the very first and important ...
241 views

### p-orbitals in STO-3G basis set

I look at the STO-3G basis set for Carbon atom (downloaded from the basissetexchange.org) and I see one set of exponents and two sets of coefficients for the p-orbitals. How do these exponents and ...
52 views

### Is this statement correct: “All structural variations are energy driven”?

In modelling using molecular mechanics can one state that "all structural variations are energy driven?". The statement is related to protein-ligand binding in modelling. Sometimes one can ...
106 views

### Are meta-GGA functionals SCAN (and its variants) ok to use in planewave DFT with the PBE pseudopotentials?

The meta-GGA SCAN functional has been there for a while. Despite the lack of SCAN (ultrasoft/PAW) pseudopotentials, various works used it in plane-wave pseudopotential calculations with ...
376 views

### When should spin polarized calculations be done?

Should the presence of a d block element in the unit cell mandate the need for performing spin-polarized calculations? I wanted to find out the DOS, PDOS, and the band structure. I'm new to DFT and I'...
21 views

### VASP's NPAR and KPAR for parallelization

What's the best way for parallelization in VASP for periodic systems? In the documentation, it mostly explains it for the local computer and molecule calculation. Apparently, these explanations don't ...
31 views

### Inconsistent data of chemical potential from different papers

I am looking for chemical potential from literature: ...
201 views

### acceptable range of stretching of a lattice unit cell when we do the heterostructure

Currently, I have to put two different materials together to form a heterostructure. I've already transformed the unit cell of material A from trigonal to cubic. Now the unit cell has a rectangular ...
63 views

### How to explain Density Functional Theory results to an experimentalist?

When we present our Density Functional Theory simulation results e.g. lattice parameters, stacking fault energies, band gaps, etc. to people who are experimentalists then the very first question ...
59 views

### Combined effects of strain and doping on the electronic structure of semiconductors

I've read papers in DFT studies on band gap tuning in semiconductors and the usually studied methods are either through doping or application of external strain. But it is always just one or the other....
128 views

### Computational biology textbook similar to “Computational Materials Science” by June Gunn Lee

I'm looking for a text for computational biology which is similar in structure to a book called Computational Materials Science by June Gunn Lee. In his book, Lee discusses the theory of MD ...