Subdiscipline of theoretical physics which consists in the study of physics problems using numerical algorithms. PLEASE NOTE that questions about computational methods and/or programming are OFF-TOPIC on Physics.SE.
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90 views
Looking for a good introductory-level review of pseudopotential methods
I'm looking for a good introductory-level review of pseudopotential methods. In particular, I'd like to understand how the self-consistent pseudopotential methods work.
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0answers
28 views
Energy Conservation [migrated]
I'm working on a time integration scheme for my research. As a result I have come across an interesting phenomena. Somehow, the total energy of the scheme oscillates. At any given time the total ...
2
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0answers
78 views
Difference between a Fixed Point and a Limit Point in implementations of the Renormalization Group (RNG) in Large Eddy Simulation (LES) model
In the introduction of this paper, it is explained that and how the application of a dynamic subrid scale model for turbulence into a large eddy simulation (LES) model corresponds to doing one ...
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0answers
148 views
Comparison of different ab-initio codes
One may find on the web a lot of different computational packages to perform "ab-initio" calculations of electron structure of the solids. Usually, the documentation is not quite transparent about the ...
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2answers
434 views
How do I integrate the Poisson equation to determine the electric potential along a particular direction (e.g., $z$)?
This question is a sequel of sorts to my earlier (resolved) question about a recent paper. In the paper, the authors performed molecular dynamics (MD) simulations of parallel-plate supercapacitors, ...
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2answers
89 views
How can one determine at which distance the Lennard-Jones potential reaches a given value?
My question is fairly simple, but I do need clarification on how to get the inverse of the Lennard-Jones potential V(x).
I am working with the following expression:
$$
V(x) = e\times[(R/x)^{12} ...
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3answers
337 views
Calculate kinematics of body movement from the set of spatial coordinates
Short intro
I have a set of 3D (x,y,z) spatial coordinates of arm movement obtained using motion capture system. The example set of such coordinates looks like this (rounded up):
...
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1answer
88 views
Strange Behavior in Spring Computer Model
To learn more about oscillatory motion which I am learning about in my high school physics class, I have created a computer model of a damped spring where the damping force is proportional to ...
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1answer
45 views
Computational Fluid Dynamics methods
I have read some articles about the finite difference method on a cartesian orthogonal grid. I understand how it works when Dirichlet boundary conditions are used, or when Neumann boundary conditions ...
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1answer
55 views
Deriving the change in the Helmholtz free energy in the context of the free energy perturbation method
I am reading Free Energy Calculations: Theory and Applications in Chemistry and Biology by Chipot and Pohorille. At the beginning of the text (page 19, for example), the authors define the Helmholtz ...
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1answer
90 views
reversible cellular automata
Let's suppose a cellular automaton has a value $b(r,t)$ belongs to $Q$ at site $r$ and time $t$, where $Q$ is the set of possible states at each site. Let $N(r, t)$ be the values of the states of all ...
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2answers
137 views
Why are Markov chains better than naive algorithm for Random picking?
I have a question about the problem of coming up with a random distribution of non-overlapping coins in a given two dimensional space. I don't understand why using the random sequential adsorption ...
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2answers
123 views
How to decide convergence of the ensemble average in a Monte Carlo process
I am simulating electromagnetic scattering off a rough surface. The usual process is to do a Monte Carlo simulation, which is briefly described as follows.
Generate a randomly rough surface, and ...
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1answer
240 views
Does the universe follow a general physical and computational principle of evolution?
Evolution is a principle in biology, whereby organisms evolve their ability to replicate and multiply in numbers over successive generations. From a computational point of view, the organisms employ a ...
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1answer
84 views
Parameter determining argon phase
Currently I am working a molecular simulation to determine phases of an argon NPT ensemble using Lennard Jones potential. Mainly I use the radial distribution function to determine solid, liquid, or ...
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1answer
169 views
Help: 3D visualization of magnetic field around moving point charge
The diagrams I'm able to find online only show the concentric field lines in the particle's plane, perpendicular to the motion, which of course generalizes to the cylindrical shape around a conductor. ...
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2answers
153 views
Where does Computer Science background students fit in Theoretical Physics [closed]
I am basically an Electronics student - background in computer science (that's where I want to work). I applied for an internship in USA in a research institute where the group is focused in ...
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1answer
169 views
Numerical algorithms to generate a random wavefunction from a thermal ensemble
I am seeking an algorithm to generate a random wavefunction = $\sum {c_i |\varphi _i\rangle }$ from a thermal ensemble, whose density matrix $\rho \sim e^{-\beta H}$, without the need to diagonalize ...
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1answer
155 views
What software can I use to simulate supersonic gas particle flow? [closed]
Please please help me out with this. I am trying to find a software/program that I could use the simulate the scattering effect of light when it strikes gas particles moving at supersonic speeds? ...
1
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1answer
82 views
Initial position and velocity of rocket to escape earth's gravity
I'm trying to numerically simulate a spacecraft trajectory between earth and mars. I already wrote the solar system model where the sun is at the origin of the x,y,z plane Earth and Mars are orbiting ...
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0answers
31 views
Trotter splitting and entanglement entropy
I have heard that a numerical solution to the Schrodinger equation using the Trotter splitting formula for a many-body Hamiltonian can cause an artificial increase in the entanglement entropy. I was ...
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0answers
74 views
2D quantum well energy spectrum (analytical vs numerical)
I am trying to understand the energy spectrum difference between the analytical and the approximated solution for a quantum well.
The particle is inside a box with domain $\Omega=(0,0)$X$(1,1)$. For ...
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0answers
62 views
What libraries are available for solving problems at the college physics level? [closed]
Are there any libraries available for solving problems at the level of college physics?
In particular, I'm interested in libraries for general purpose programming languages that can calculate results ...
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0answers
170 views
fun computational physics projects [closed]
I want to learn how to code in Java and am in need of some cool computational physics projects that would provide motivation to do so. I was wondering if you guys could list some medium-level ...
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0answers
35 views
bond energies database [closed]
I’m looking for a public database of bond energies of biochemical compounds. Do you know about any?
Otherwise, which is the standard computational methodology to calculate them? Any references would ...
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0answers
367 views
Calculating semi-major axis of binary stars from velocity, position and mass
I'm trying to calculate the 'instantaneous' semi-major axis of a binary system with two equal (known) mass stars for an $N$-body simulation. I know their velocities and positions at a given time, but ...
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0answers
141 views
Modeling the trajectory of a particle in an Electric field [closed]
[This problem has been resolved, sorry for posting in the wrong forum!]
(I was trying to model the trajectory of a particle in an electric field.)
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1answer
162 views
Boundary condition for water waves generation
I am trying to model water wave propagation in 2D with CFD. What would be a suitable boundary condition to generate the waves on the left boundary? Currently I vary the fraction of water above the ...
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0answers
100 views
Calculating collisions in realtime - dealing with a delay in time [closed]
I wasn't sure in which stackexchange to post this, since the questions deals with a lot of different topics. I've posted it first at stackoverflow, but I've been redirected here...
Suppose:
You're ...
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1answer
193 views
How is acceleration computed in the leap-frog algorithm in computer simulations of particles?
I am reading the book Computer Simulation of Liquids by Allen and Tildesley (here is another link). On page 80, the authors describe the leap-frog algorithm, which is used extensively in molecular ...
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1answer
79 views
Magnetic field of permanent magnet [closed]
Hi I am looking for some code to (computationally) calculate the magnetic field of a rectangular permanent magnet in 3D space. Preferably I could edit it to add in my own dimensions. Does anyone know ...
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1answer
395 views
Calculating Kramers-Kronig using Mathematica
First of all, I know there is a Mathematica group in beta, but I don't think the problem of the following is directly a Mathematica issue.
I am trying to calculate the change of the refractive index ...
0
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1answer
146 views
Filtering and extracting turbulent data from instantaneous dataset
I have collected data on flow velocity at 1 Hz sampling rate for 25 hours using a high resolution acoustic Doppler current profiler (HR-ADCP).
how I can decide up to which period is the mean ...
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0answers
14 views
Spring damper model does not work very well [migrated]
I'm trying to model a spring damper system from a tutorial that I've found on this site.
If I use the exact same parameters as the ones in the tutorial the system is not stable. I've downloaded the ...
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0answers
6 views
Finite Element, NASTRAN, how to print the differential stiffness matrix in .f06 output file [migrated]
We are working on an optimization problem in which we can approximate the eigenvalue calculation by assuming a constant eigenvector, using the formula:
$$
...
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0answers
12 views
Calculation of translational free energy in condensed phase
For gases, the reference volume in molecular calculations is usually understood to be 24.5 L whereas in solution, the reference volume usually is considered to be 1 L.
The free energy corrections ...
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0answers
16 views
Implementing Explicit formulation of 1D wave equation in Matlab #FiniteElements #FiniteDifferences [migrated]
so the theory is straight forward.
we have:
$\frac{d^2U}{(\Delta t)^2}=c^2 \frac{d^2U}{(\Delta x)^2}$
discretizing it gives:
$\frac{U(i+1,j)- 2U(i,j) + U(i-1,j)}{(\Delta t)^2} = c^2 ...
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45 views
numerical investigation of stability [closed]
I am trying to find the required specifications of an paul RF trap, in which a proton can be confined.(trap dimensions,voltage frequency and amplitude used, etc). I have to solve the equations of ...
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112 views
Physics problems requiring numerical solutions to polynomial systems? [closed]
This is a very general/open-ended question.
I wonder if numerical solutions to large scale system of polynomial equations (in many variables) are used in physics at all. I am looking for some good ...
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76 views
Coupled decay behavior? [closed]
I solved the following "coupled" ODE numerically, whit forward Euler scheme:
$$
\frac{\text{d}N_a}{\text{d}t} = -\frac{N_a}{\tau_a}
$$
$$
\frac{\text{d}N_b}{\text{d}t} = ...
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54 views
Is it possible to use the properties of quantum mechnics to develop a computer that develop mathmatical theory? [closed]
Is it possible to use the properties of quantum mechnics to develop a computer that develop mathmatical theory?
I want some reference please, because i want to get into very detailed.
Thanks in ...
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0answers
142 views
Quantum Compting or DNA computing [closed]
My friend and me are working on DNA computing and on some improvements to it.
Of course, we are working on computing aspects of this branch. So, we have insufficient knowledge about physics and ...
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74 views
References for circular restricted 3 body problem?
Does anyone know of any good references for the CR3BP -- the circular restricted 3 body problem? Emphasizing on real-life applications, and interpretation of the numerical solutions? Thank you. There ...
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1answer
139 views
Mathematica( Computational physics) [closed]
Make a procedure to count change. Initially, you may use Us currency, where a quarter is 25 cents, a dime is 10 cents, a nickel 5 cent, and penny is 1 cent. Given any amount of money, determine how ...
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2answers
52 views
Standards for scientific metadata in common-use image formats? [closed]
I have a bunch of JPEG, JPEG2000 GIF and PNG files that in theory could be used for some types of science analysis if there were temporal and spatial information in them.
Years ago, I had looked into ...
