Questions tagged [correlation-functions]

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3 votes
1 answer
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Effect of trajectory length and resolution on the Residence Time

I have tried to calculate Residence time using the residence time auto-correlation function defined as $$R(t) = \frac{\langle h(0)h(t)\rangle}{\langle h(0)h(0)\rangle}$$ In the calculation, I have ...
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7 votes
0 answers
46 views

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

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 ...
  • 629
7 votes
1 answer
117 views

VdW-D3 correction with HSE06 functional in VASP

I am trying to account for Vander waals correction in VASP. Now doing this for PBE is easy all one has to do is set IVDW=11 but the VASP webpage for DFT-D3 says ...
  • 629
5 votes
1 answer
225 views

Programming auto-correlation function calculation

I have a set of data (heat flow) values in x, y and z directions for which I have to calculate the auto-correlation function to get the thermal conductivity. I have written a small Fortran90 code but ...
  • 91
7 votes
0 answers
135 views

Diffusion coefficient as a function of distance from the position autocorrelation function [closed]

I am trying to understand if my idea for the computation of diffusion coefficient as a function of distance is right or not. So, the diffusion coefficient as a function of distance is given by, $$D(z) ...
9 votes
1 answer
249 views

What is autocorrelation time?

I'm writing this code of molecular dynamics about a pseudo-ideal gas in a box. The task is integrating the EOM for every atoms for a time-step dt fixed with the leapfrog method and measure the total ...
7 votes
0 answers
81 views

How to use the HNC approximation to find the change in grand potential

I am reading Hansen and MacDonald's Theory of Simple Liquids, and I am going through Integral Equation theories. In section 4.3, they put forward the equation (4.3.14), $${\small \Omega _{\phi} = \...
  • 4,091
7 votes
0 answers
257 views

What's the pair correlation function? What information does it contain? [closed]

This question is related to this VASP tutorial, in which the pair correlation function (or radial distribution function: RDF) is utilized to justify whether the solid silicon is melt by AIMD (ab-...
  • 14.6k
9 votes
1 answer
149 views

Derivation on correlation function and response functions in polymer physics

I am reading Introduction to Polymer Physics by Doi and I am having trouble understanding a derivation by him on the concentration fluctuations in polymer solutions. I have outlined his method and ...
  • 4,091
7 votes
0 answers
99 views

Deriving relations for a hard sphere phase diagram [closed]

In Torquato's book "Random Heterogeneous Materials", he has written: $$\frac{p}{\rho kT} = 1+2^{d-1}\eta g_2 (D^{+})\tag{1}$$ where $g_2(D^+)$ is the contact value from the right-side of the ...
  • 4,091
22 votes
1 answer
1k views

How exactly does one compute the vibrational density of states from the output of a molecular dynamics simulation?

There are many things that can be done with the output of a molecular dynamics simulation, but one of the more powerful things is the ability to compute the vibrational density of states (or the ...
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12 votes
0 answers
136 views

Correlation Functions in the Cluster Variation Method [closed]

I've been referring to Dr Mohri's paper [DOI: 10.1007/s11837-013-0738-5] for the cluster variation method (CVM). I wish to calculate the configurational entropy of a binary FCC system. Cluster ...