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# Matter Modeling : Recent Questions and Answers (Page 5)

## What are typical RPA capabilities of plane-wave codes?

Plenty of standard plane-wave codes are able to compute correlation energies on top of DFT solutions using the random-phase approximation (RPA). I was wondering what the typical capabilities are in...

Asked on 08/19/2021 by Michael F. Herbst

## Quadrature over three Euler Angles for orientation averaging

Does anybody know about an accurate quadrature rule over three Euler angles $theta, phi, chi$?I am trying to calculate the average value of an arbitrary function \$f(theta,...

Asked on 08/19/2021 by Emil Zak

## What are some open-source all-electron DFT alternatives to Wien2K?

Since the beginning of the century, Wien2K has proven to be a very powerful player in computational condensed matter and materials physics. Wien2K is an all-electron periodic DFT...

## Real space projection vs reciprocal space projection in DFT calculations

When doing VASP calculations for large cells, we get a warning:"You have a (more or less) 'large supercell' and for larger cells itmight be more efficient to use real...

## How to calculate the Fock matrix in the molecular orbital basis PySCF?

I am interested in calculating the Fock matrix in the molecular orbital basis with PySCF, though I am not clear on the methodology behind this task.In my attempt, I...

## Bond Order: When and how is it used today?

We all learned about single vs double vs triple bonds in high school chemistry and biology. We learned that unsaturated fats have double bonds whereas saturated fats have only single...

## Is it possible to calculate/estimate the value of the J parameter to be used in the Heisenberg/Ising Hamiltonians?

Studying magnetic systems, two frequently used approximations are the Heisenberg and Ising models (a discussion about these approximations can be read here): begin{equation}tag{Heisenberg}hat{H}_H=-sum_{langle i jrangle}Jhat{S}_ihat{S}_jend{equation}...

## What are some methods for modeling bulk phase infrared spectra?

I am interested in predicting the infrared spectra of bulk phase molecules, it seems that AIMD (ab initio molecular dynamics) is the current best approach. I have found a tutorial...

## What is the closest thing we have to "the" universal density functional?

It is understood that finding "the" universal functional is an NP-complete problem. However, progressively better functionals have been constructed decade after decade and fitted to more and more comprehensive datasets....

## Molden installation on macOS?

Today I tried to get an access to Molden to install it and use for processing the results of my calculations. Unfortunately the ftp seems to be down or is...

Asked on 08/19/2021 by Dmitry Eremin