# Tag Info

## Hot answers tagged soft-question

25

It depends on what chips datacenters are using. If large data centers switch over to ARM-based processors, scientific computing will follow. Since most of our software is open source (or not far from that), converting to ARM compatibility will not be too much of an issue once the demand is there. Scientific computing is currently dominated by enterprise-...

16

I'd expect that x86_64 will remain the architecture of choice for computing throughput for quite a while, and that there might even be a way to deliberately re-enable the Spectre/Meltdown vulnerabilities because they give a nice speed boost and are irrelevant if you don't share the CPU with anyone else. ARM shines in the datacenter because a lot of the work ...

16

I'm just as curious of a user here as you, but I was able to find that a Materials Modeling Wikipedia page does in fact exist. :) Computational materials science and engineering uses modeling, simulation, theory, and informatics to understand materials. Main goals include discovering new materials, determining material behavior and mechanisms, ...

16

As evident from the name, Materials Modelling (or Computational Materials Science as it is sometimes called) lies at the intersection of materials science and computational engineering. To answer this question, the level of education required depends entirely on what one intends to do with materials modelling. Materials science is quite interdisciplinary, ...

15

In the paper "A Continued-Fraction Representation of the Time-Correlation Functions", generalized susceptibilities and transport coefficients for materials are obtained using a continued-fraction expansion of the Laplace transform of the time-correlation functions. This was the precursor to what is now called the "hierarchical equations of ...

13

EDIT Doing what you want is hard! You will need a full quantum mechanics based simulation. This is unlikely to be something you can build yourself at the current time. Based on your new additions to the question what you need is Car-Parrinello or Born Oppenheimer MD. These essentially automate the idea of do a quantum electronic structure calculation, take ...

13

You may take a look at the Method of Continued Fractions used in quantum scattering theory—this was only formed in 19831 so is rather recent. Related is the PhD thesis by Kónya (2000)2; §3.3 onwards. Reference [1] Horáček, J., Sasakawa, T. (1983). Method of continued fractions with application to atomic physics. Physical Review A. 28(4):2151–2156....

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I think that it is not the education per se (a Masters or PhD in Physics or Chemistry, for example), but the set of disciplines you take that will help you to better understand and work in the Materials Modeling area. Courses like Classical Mechanics, Electromagnetism, Quantum Mechanics, Statistical Mechanics and Solid State Physics are fundamental. Also, ...

13

Answering your last questions: yes, yes and yes. One thing to consider is which approach do you want/need to use. You can use an atomistic approach where you simulate/model the properties and the material starting from the atomic structure of it (an input file with the list of atoms and its coordinates). The other approach is to use your material as a ...

12

Any code that does not have core parts written in machine level code (assembly) is going to be portable to arm64 straight away; you just have to recompile the program. This is the whole point of having programming languages in the first place: you need to be able to run your program on different architectures without rewriting the program from scratch, like ...

12

The only proper way to do it ab initio is to calculate the energy (E) for various internuclear distances (R) and then to approximate the equilibrium bond length by choosing the distance which has the lowest energy, or by fitting the E(R) points to something like a Morse potential (which is decent for short-distances), Lennard-Jones potential (which is decent ...

11

Generally speaking, most work in molecular dynamics tries to simulate how actual molecules behave (i.e. quantum mechanics) and it doesn't sound like you want to go down that rabbit hole. I completely agree, but I'll begin with a disclaimer that looking up "molecular dynamics" probably won't turn up the kind of results you want. Since your comments ...

11

How to proceed depends on how accurate you want the outcome. Throughout my answer I will provide blue buttons which demonstrate that there's entire tags in our community to address certain aspects of the simulation. What you are describing is (essentially) what we call molecular-dynamics even though you're dealing with atoms rather than molecules. In MD (...

10

It's a very good question, and we may get several answers here from people with various different perspectives, but here is mine: In every case so far where we are certain that computations have been done thoroughly enough, known quantum field theories have been able to reproduce experiments when gravity is not strong enough to play a role. For example, QED (...

9

In order to simulate two atom interaction, you have different path to follow. One is to use Density Functional Theory (DFT) or ab initio, make a script where the distance of the atoms is decreasing, and for each distance, you calculate the system energy. The image below is the result of such calculation but between a metal atom and a carbon nanotube1. You ...

8

While this earlier question on our site was asking why fewer 2e- integrals were printed by PySCF than expected, and your question is simply asking how to calculate the 1e- and 2e- integrals in the first place (so the two questions are not duplicated), that question gave an excellent example for how to print the 2e- integrals for the He atom in a 6-31g basis ...

7

Unfortunately the answer to this question is much the same as your last one. What you are trying to do is hard. Very hard. Creating this would be PhD if not postdoc work and doing it well could well win you a nobel prize. From the comments you've made in this and your other question you do not appear to be a specialist in either physics or chemistry, and ...

7

The simplest possible atomic simulation: a noble gas As explained by Nike Dattani, what method you use depends on what you want to simulate and why. He gives you a good roadmap for what method to choose based on what you want to do. I wanted to take a different perspective. If you're familiar with writing code and want to program the simulation yourself, ...

7

The main difference between ARM64 and x86_64 architectures is their core design. The x86_64 uses NUMA when more cores are involved, whereas ARM64 has a more versatile design, and can have unified memory access. The ARM64 design is less complex than the x86_64, and for highly parallel computing, a simpler design may help the performance. I see at least two ...

6

Same as any other electronic structure code: atomic units are used. The unit of energy is Hartree, $E_h$, in which the ground state energy of hydrogen is exactly $-0.5$. One Hartree is roughly 27.211 386 245 988 eV, see the NIST database. The atomic unit for length is the Bohr radius, $a_0$. Defining things in terms of atomic units has the huge advantage ...

6

One thing to be absolutely clear from the beginning is that there is no simple theory of the chemical bonding between two atoms. We do understand a whole lot about the physics that goes into this process, but the physical understanding is not really transformable to formulas that could be reasonably evaluated. Hell, theoretical physicists are still working ...

5

Get your parameters from an existing force field (UFF? ReaxFF?) People in the molecular dynamics world use established force fields to describe forces between different types of atoms. These force fields are mathematical functions that have parameters like bond lengths, bond angles, dihedrals, van der Waals radii, etc. Usually these parameters are obtained ...

5

I don't know why you need atom-atom interactions in a sandbox game. My only guess is that you want to simulate or visualize the movement of molecules of some kind in real time. If your system is large i.e. more than ~20 atoms, you have to resort to molecular dynamics to get reasonable speed. This has already been covered in detail in Max's answer, so I will ...

5

The continued fraction expansion is the most common way to calculate real-frequency dynamical Green's functions using Lanczos exact diagonalization. The method was introduced in this setting in Gagliano, E. R., and Balseiro, C. A., "Dynamical Properties of Quantum Many-Body Systems at Zero Temperature," Physical Review Letters 59, 2999 (1987), but ...

4

ARM64 may not have to be the next big thing to cause a positive change. Competition between two standards could result in extensions of either standard to improve them. We already see vendor specific extensions making a big difference with intel vs amd for example. From what I have seen, as long as the software support is good (as others have pointed out, ...

4

The most trivial model to estimate bond lengths between two atoms is probably a simple sum of Van-der-Waals Radii. Just load a table with Van-der-Waals Radii and take the equilibrium distance for two atoms as the sum of the Van-der-Waals Radii of both atoms. This is by no means accurate but for the intention of the poster it might suffice. If this is still ...

3

I don't think you are looking for anything too physically correct so I think for your purposes, you can get away with a simple morse model. Consider which elements you would like to use, hopefully you can restrict it to basic organic elements such as C,O,N,H,Cl,B and consider which elements that need to be able to bond together. Prepare a table such that you ...

3

When I read your question I remembered a gitlab pages that list all the softwares ported to the arm architecture and their development progress. You can find it here: https://gitlab.com/arm-hpc/packages/-/wikis/categories/allPackages Hope this can help.

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