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Questions tagged [optical-properties]

Questions about optical properties.

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How to calculate the volume energy loss function (VELF) using Quantum ESPRESSO?

How to calculate the volume energy loss function (VELF)? Could you please share with a simple example (with related input files, output files and/or plot)? Any relevant links would also be welcome.
Sak's user avatar
  • 969
3 votes
0 answers
26 views

Quantum ESPRESSO: how to calculate mobility?

How to calculate the mobility? Could you please share with a simple example (or simpler equation) to do this? Or in other words, if we have $E_g$, $E_F$, $P$, $V_{cell}$, $E_{vb,max}$, $E_{vb,min}$, $\...
Sak's user avatar
  • 969
2 votes
0 answers
28 views

Methods of convergence in GW-BSE calculations: Quantum ESPRESSO and BerkleyGW

I have been learning BSE calculation through Quantum ESPRESSO and BerkeleyGW. I have been successful to obtain the silicon optical spectra (via GW-BSE), as instructed in the tutorial. The values of ...
Sak's user avatar
  • 969
6 votes
0 answers
17 views

Calculate IR refractive index (NK)

I'm a new user of Materials Studio and trying to use CASTEP to calculate the IR refractive index of $\ce{SiO_2}$, in which optical phonon effects are very important. Experimental data shows an ...
TIANREN YU's user avatar
4 votes
1 answer
38 views
+50

How to convert epsilon_2 to absorbance in optical calculation? DFT, RPA, Quantum ESPRESSO

I have a calculation via DFT-RPA, which calculates epsilon_2 and energy (eV). For optical property calculation, we usually plot epsilon_2 vs energy (eV). However, I need to know to convert the y-axis ...
Sak's user avatar
  • 969
3 votes
0 answers
30 views

Error in ph.x file

I ran this ph.x file for my structure. However, this response error was displayed. Observation: I made my scf file with norm conserving pseudopotential. The result was ok. Input: ...
Caroline Santos 's user avatar
4 votes
0 answers
34 views

Calculating excitonic optical properties with BSE level in VASP

I have been working on 2D material systems and their heterostructures. While calculating BSE excitonic optical properties in VASP, I encountered that the 2D material property is well matched with ...
Hydronics Lab's user avatar
2 votes
1 answer
50 views

optical properties in IR region

I have done geometry optimization using hybrid functional. this gives a band gap that is comparable to the experimental one. but I am also expecting my optical properties to be in IR region, but they ...
Noor's user avatar
  • 45
3 votes
0 answers
20 views

How to construct the input files to obtain the structural measurements using Quntum Espresso?

I'm working with a SiPOCa structure and I've already done the SCF, NSCF, DOS, BANDS, CHARGE DENSITY, FTIR and RAMAN calculations. Now I would like to calculate the structural measurements of this ...
Caroline Santos 's user avatar
5 votes
0 answers
87 views

Optical properties using ESPRESSO's epsilon.x

Currently I'm using epsilon.x from Quantum ESPRESSO to analyse optical properties of metallic alloys. I'm getting a wiggling curve for the dielectric function. For the imaginary part of dielectric ...
Anibal Bezerra's user avatar
3 votes
0 answers
26 views

Compare transition matrix elements in molecules and solids

Is there a general trend such that transition matrix elements for electronic/excitonic transitions are larger/smaller in molecules than in inorganic solids or vice versa?
freude's user avatar
  • 392
4 votes
0 answers
44 views

supercell nscf kpoints for optical properties

I am calculating the optical properties of 200 atoms supercell with quantum espresso. What is the approximate number of the nscf kpoints (nk nk nk)should I start with, to avoid lengthy kpoints ...
hakou elhaj's user avatar
5 votes
0 answers
83 views

Packages that can model effects of intense electric fields from femtosecond compressed IR and EUV laser pulses on surfaces?

Laser-based and time-resolved ARPES are relatively1 new techniques to study atomic and especially electronic structure (necessarily) near crystal surfaces and of adsorbed 2D materials on those ...
uhoh's user avatar
  • 2,034
6 votes
1 answer
922 views

Optical proprieties with Quantum espresso

I am a beginner in Quantum Espresso, and I want to calculate optical properties. When I calculate the dielectric functions, it gives me four output files. I don't know which files correspond to the ...
SOELHADFI's user avatar
  • 433
3 votes
1 answer
377 views

Absorption coefficient from dielectric function

I am aware that one can compute absorption coefficient ($\alpha$) from the dielectric function with the equation $\alpha$ = $(4*pi*k$)/$\lambda$ … (1) Or from the equation $\alpha$ = k*$\omega$ … (2)...
Musa Usman Sarki's user avatar
6 votes
0 answers
48 views

Benchmarking DFT vs Experimental Gaps - Confusion over Fundamental and Optical Gaps

Recently, I've come across discussions about the differences between fundamental (or electronic) bandgaps and optical bandgaps, with the two quantities differing mainly by the electron-hole binding ...
CW Tan's user avatar
  • 1,306
4 votes
0 answers
119 views

Why my scf calculation with 30*30*30 k-points grid is stuck in the same line for more than 6 hours? [closed]

I'm running a scf Quantum ESPRESSO calculation on a cluster to get the optical properties of my material. I noticed that the output file is stuck in the same line for more than 6 hours even though ...
Camilla's user avatar
  • 2,159
3 votes
0 answers
43 views

Weighted average optical spectra in VASP

I am working on a 2D system where geometric and magnetic isomers are energetically very close to each other (orders of meV). I am interested in optical absorbance spectra using GW+BSE approach but I ...
Gallifreden's user avatar
2 votes
0 answers
149 views

Query about optical data extraction using Vaspkit

Recently I tried to extract the optical absorption data using Vaspkit (vaspkit.1.3.0/vaspkit.1.3.5]). I performed the optical calculations of one 2d system along with SOC using VASP. While extracting ...
Poonam Sharma's user avatar
2 votes
0 answers
37 views

Which component of the dielectric tensor is used in generating EELS in TDDFT? [closed]

Electron Energy Loss Spectroscopy (EELS) comes from the imaginary part of the inverse dielectric function $-\text{Im}[\varepsilon^{-1}(q, \omega)]$. If the dielectric function is actually a tensor and ...
electronblue's user avatar
4 votes
1 answer
108 views

Why my values of dielectric function don't match litterature (For Yambo with Quantum ESPRESSO)?

I try to reproduce the dielectric function as the picture bellow using Yambo code but the values that I have found in y-axis are so much bigger [-1000,1500] compared to literature. I generated the scf ...
Camilla's user avatar
  • 2,159
5 votes
1 answer
129 views

How to plot the dielectric function calculated with Yambo?

I want to calculate the optical properties using Yambo. I used Quantum ESPRESSO 7.0 with Yambo 5.1.0, but I'm facing an issue. When I generate the dielectric function (o.eps_q1_ip) for example the o....
Camilla's user avatar
  • 2,159
3 votes
1 answer
249 views

Would it be appropriate to use a Van der Waals-DFT approximation in Quantum ESPRESSO to study the properties of my material (p-type semiconductor)?

I want to study the structural, optical, electronic and transport properties of my material that contains Cu atoms using Quantum ESPRESSO. I tried so many approximations but every time I face an issue ...
Camilla's user avatar
  • 2,159
5 votes
1 answer
586 views

Why does my zincblende structure not look cubic?

The structure of my material is zincblende. So normally the structure is cubic. However, when I open the primitive cell with xcrysden it dosen't look 100% cubic. It's a little bit inclined. Also when ...
Camilla's user avatar
  • 2,159
4 votes
0 answers
128 views

Absorption spectra with Gaussian [closed]

I want to calculate the absorption spectra of molecules (and possibly ions) with TD-DFT. I have used Gaussian in the past and, to my knowledge, the application of TD-DFT is implemented in this code. ...
Laura's user avatar
  • 1,267
8 votes
0 answers
95 views

Which Exchange Correlational Functional should be chosen for calculation of optical properties in VASP using LOPTICS tag? [closed]

I am planning on calculating optical properties mainly dielectric constant using LOPTICS tag in VASP. Now for my electronic calculations I have been using HSE06 mainly because of higher accuracy of ...
Chan's user avatar
  • 649
6 votes
2 answers
385 views

Optical Band gap determination from absorption coeffecient using DFT

I am currently working with a perovskite material which shows forbidden transitions. Older studies used bigger values of $\alpha$ in HSE06 calcualtions(to match with experimental Band Gap) but a ...
Chan's user avatar
  • 649
2 votes
1 answer
430 views

Studying computing on HSE06 in VASP

I optimized the structure in PBE. Can anyone help me with HSE06 to calculate the optics and DOS of the material from this step? I would be grateful if you could write step by step.
Davron Kurbanov's user avatar
4 votes
1 answer
94 views

Query about optical absorption spectra

I have one query about data obtained in the optical calculation (absorption coefficient) using GGA. The output came in the format energy xx yy zz xy yz zx for bulk system. I have seen in the ...
Poonam Sharma's user avatar
8 votes
0 answers
347 views

How to find Optical Property in VASP using HSE functionals? [closed]

I have calculated frequency-dependent dielectric constant in VASP using PBE exchange-correlation functional, within the framework of Independent particle approximation (with RPA). I want to perform ...
problem_guy's user avatar
4 votes
1 answer
379 views

Evaluating absorption coefficient using VASPKIT for nanostructures (specifically quantum dots)

I was planning to use VASPKIT in order to determine the linear optical properties of my nanostructure. But upon running VASPKIT, I do not see an option for 0D materials but only for 2D and bulk. Is ...
Parmeet Singh EP 066's user avatar
10 votes
2 answers
91 views

Optical spectra beyond electric dipole approximation

I'm wondering what are the typical examples (experiments) for magnetic dipole transitions and electric quadrupole transitions in crystals?
Xiaoming Wang's user avatar
4 votes
1 answer
587 views

Optical properties without LOPTICS tag

I have performed some calculations for a 2D-monolayer using VASP. I run DOS calculations without LOPTICS = .TRUE. I found that ...
astha's user avatar
  • 1,673
8 votes
2 answers
240 views

Can the color of gold metal be reproduced by modeling only the conduction electron band structure, or do atomic absorption lines contribute?

@JohnCuster's answer to Why is gold golden? is based on the band structure of the delocalized conduction electrons in gold, whereas other answers there tend to support the "Gold is gold due to ...
uhoh's user avatar
  • 2,034
7 votes
2 answers
467 views

Why is there a large discrepancy between calculated frequency dependent dielectric function and experimental measurement?

I am calculating the frequency dependent dielectric function of $\ce{SiC}$ using VASP. After a geometry optimization, the INCAR file below is used for the ...
Achintha Ihalage's user avatar
4 votes
1 answer
106 views

Optical anisotropy from first-principles

I am interested in the theoretical study of optical anisotropy (birefringence, dichroism etc.) of different materials. I have seen DFT works studying optical anisotropy from the calculation of ...
Thomas's user avatar
  • 9,132
8 votes
3 answers
886 views

Why can't we change the spin angular momentum of electrons with an external optical field?

I have read this paper many times: Coupled Spin and Valley Physics in Monolayers of MoS2 and Other Group-VI Dichalcogenides. Interestingly, this paper is also discussed many times in this community, ...
Jack's user avatar
  • 15.2k
11 votes
1 answer
1k views

DFT optical calculation and plotting for real and imaginary permittivity in VASP?

I have calculated Frequency dependent optical permittivity of Au using (VASP) my INCAR tag includes LOPTICS=.TURE., my OUTCAR ...
CH M. Usman Javed's user avatar
9 votes
1 answer
615 views

A good software for DFT optimization and nonlinear optical properties

I'm running a series of calculation for nonlinear chromophores. The general pipeline is geometry optimization (B3LYP/def2-TZVP) -> Frequencies -> Hyperpolarizability calculation (M06-2X (or CAM-...
Roman's user avatar
  • 2,373
12 votes
1 answer
262 views

Why linear response is absent in a non-centrosymmetric system with time reversal symmetry?

In this paper, it is mentioned that a non-centrosymmetric system with time-reversal symmetry doesn't have a linear response. It is actually a consequence of the Onsager reciprocal theorem. But I didn'...
walber97's user avatar
  • 447
11 votes
1 answer
347 views

Calculating hyperpolarizability in NWChem

I'm trying to make a pipeline geometry optimization -> calculation of polarizability/hyperpolarizability. And NWChem seems pretty good for it, the only thing I can't understand its how to calculate ...
Roman's user avatar
  • 2,373
11 votes
1 answer
180 views

How can we make a mechanically unstable cubic system, stable

I have to calculate the elastic constants of a Cubic system using a Density functional theory-based software. A cubic system will be mechanically stable if it satisfies the Born-stability condition (...
astha's user avatar
  • 1,673
16 votes
2 answers
2k views

How to start with the optical properties of 2D materials with the VASP code?

I hope you are doing well. I am new to VASP, and my project is "Optical properties of 2D materials on VASP" but I have no idea how to run a simple calculation with VASP. I will be very ...
Haris's user avatar
  • 229
11 votes
1 answer
244 views

Are there any other options beyond increasing the k-sampling and the number of unoccupied bands, to achieve better results?

I am trying to determine the optical properties of bulk Aluminium and related alloys using Quantum ESPRESSO. I am using both the epsilon.x and the simple.x modules to get wavelength-dependent ...
Anibal Bezerra's user avatar
5 votes
1 answer
1k views

How to implement scissor-correction in VASP to study optical properties?

It is mentioned here that It is possible to correct for the DFT band gap error by introducing an empirical scissors correction, which is effectively a rigid shift of the conduction band with respect ...
Thomas's user avatar
  • 9,132