What is Gaussian: Definition and 771 Discussions

Gaussian is a general purpose computational chemistry software package initially released in 1970 by John Pople and his research group at Carnegie Mellon University as Gaussian 70. It has been continuously updated since then. The name originates from Pople's use of Gaussian orbitals to speed up molecular electronic structure calculations as opposed to using Slater-type orbitals, a choice made to improve performance on the limited computing capacities of then-current computer hardware for Hartree–Fock calculations. The current version of the program is Gaussian 16. Originally available through the Quantum Chemistry Program Exchange, it was later licensed out of Carnegie Mellon University, and since 1987 has been developed and licensed by Gaussian, Inc.

View More On Wikipedia.org
Recent contents Top users
  1. L

    Help with Gaussian Calc: P_Sigma & P_Pi Overlap Integrals

    Hello Forum, Gaussian novice here with some experience of GaussView. I want to use the Gaussian software to calculate the p_sigma and p_pi overlap integrals for some metal/noble gas combinations. We do not have Foresman and Frisch in our university library and I wanted to...
  2. A

    Chi Squared and Gaussian Population Question

    The following data represent a frequency distribution of 200 variables drawn from a parent Gaussian population with mean=26.00 and standard deviation=5.00. the bins are 2 units wide and the lower edge of the first bin is at x=14. 4;8;11;20;26;31;29;22;26;13;5;2;3 a. plot a histogram of these...
  3. I

    Correlated multivariable gaussian random number generation

    \mathrm{prob} \propto \mathrm{e}^{-\frac{(a -x_1)^2}{2 \sigma^2}} \mathrm{e}^{-\frac{(x_1 -x_2)^2}{2 \sigma^2}} \mathrm{e}^{-\frac{(x_2 -x_3)^2}{2 \sigma^2}} \mathrm{e}^{-\frac{(x_3 -b)^2}{2 \sigma^2}} a and b are known real constants. Is there a way to generate x_1, x_2, x_3 independently...
  4. H

    Gaussian Elimination Solution to the 2D Poisson Equation

    I am trying to use Gaussian elimination to solve the 2D poisson equation. I've done this for the 1D problem without problems, but for some reason my solution for the 2D problem is incorrect; it looks something like the correct solution but it's as if the resulting field were cut in half, so...
  5. A

    Inner product of random Gaussian vector

    Hi, I would like to ask a question please. Assume we have a random vector X that is distributed under the Gaussian model and take the inner product of this vector and another constant vector d. Will the source distribution (Gaussian) remain the same? My intuition (although I might be...
  6. N

    How do you do a gaussian integral when it contains a heaviside function?

    How do you do a gaussian integral when it contains a heaviside function!? Very few textbooks cover gaussian integrals effectively. This isn't a big deal as they are easy to locate in integral tables, but something I cannot find anywhere is how to handle a gaussian with a heaviside heaviside...
  7. D

    Time Evolution of Gaussian Wave Packet in Anisotropic Harmonic Oscillator

    Homework Statement So this kinda incorporates my last questions. I have a particle described by a Gaussian wave packet. And it moves in 2D anisotropic h.o potential with commensurate frequencies (1:2). I've solved the x part (I was messing around with the nasty integral, which in the end...
  8. D

    Question about Gaussian wave package

    Homework Statement At t=0 the particle is localized around x=x_0 that is: \langle x\rangle (0)=x_0, and the impulse is: \langle p\rangle (0)=\hbar k_0, we can describe the particle with the wave function: \psi(x,0)=Ae^{-\frac{(x-x_0)^2}{2\sigma^2}+ik_0(x-x_0)} Now, my question is: If I...
  9. P

    Finding Perpendicular Vectors in R^4 Using Gaussian Elimination

    Find all vectors in R^4 that are perpendicular to the three coloumn vectors [1 1 1 1], [1 2 3 4], [1 9 9 7] sorry i don't know how to make them verticle guassian elimination or Ax=b I know that the dot product must equal 0 but I am not sure how to solve it
  10. E

    How to compute Gaussian Quadrature weights?

    My numerical analysis book doesn't explain it. It just tells you to use precomputed tables, and directs you to an out of print book from the 80's that I can't find anywhere. After searching, I found http://en.wikipedia.org/wiki/Gaussian_quadrature#Computation_of_Gaussian_quadrature_rules" in...
  11. A

    A Gaussian beam is passing through a 2-lense system:

    Homework Statement The first lense has a shorter focal length than the second (f1/f2 The waist of the incoming beam is very far from the lense compared to the focal length & Rayleigh range. What distance between the two lenses would provide the best collimation (Rayleigh range) for the...
  12. A

    Mean tends Infinity in Gaussian Case

    Hi, I am wondering what happens to a Gaussian distribution when its mean tends to infinity. By looking at the equation of a Gaussian one might infer that the limit will go to zero; but does this imply that it reduces to a Dirac-Delta function? More precisely, if we integrate this limit we...
  13. P

    Electric Flux through a Gaussian Surface

    Hi all, I need your help with a question. Here goes, Homework Statement There is a hollow conducting sphere with a uniform surface charge density of +\sigma. A charge -q, is placed inside the cavity of the hollow sphere. What is the electric flux through a spherical surface just inside...
  14. Y

    Rules for gaussian random variables - ornstein uhlenbeck process

    Homework Statement The Langevin equation for the Ornstein-Uhlenbeck process is \dot{x} = -\kappa x(t) + \eta (t) where the noise \eta has azero mean and variance <\eta (t)\eta (t')> = 2D(t-t')\delta with D \equiv kT/M\gamma. Assume the process was started at t0 = - \infty. Using...
  15. E

    Gauss' Law and gaussian surface

    Hey there, just had a question about Gauss' law, should be relativity simple however the explanation we were given was quite poor and only seems to apply well to the examples we were given. (This isn't homework). I (think I ) know the equation for Gauss' Law and what it means, that basically...
  16. R

    Dirac Delta as Gaussian functions

    I am looking at a problem, part of which deals with expressing delta dirac as a limiting case of gaussian function. I am aware of the standard ways of doing it. In addition, I would also like to know if the following are correct - \delta(x-a) = \lim_{\sigma \rightarrow{0}} \int_{a -...
  17. B

    Matlab Code Help - Gaussian Function

    -------------------------------------------------------------------------------- Hello, I am new to this forum so please kindly let me know if my question needs to be posted in another area. I am trying to write a MATLAB code to show a chirped Gaussian function and I am having some...
  18. B

    Matlab code help - Gaussian Function

    Hello, I am new to this forum so please kindly let me know if my question needs to be posted in another area. I am trying to write a MATLAB code to show a chirped Gaussian function and I am having some trouble with it. I am trying to obtain a chirped Gaussian pulse by modulating a chirped...
  19. W

    Understanding the Evolution of a Gaussian Wave Packet

    Homework Statement Calculate \Psi(x, t) for the gaussian wave packet according to the amplitude distribution function a(k)=C*\alpha*e^{-\alpha^2k^2}/ \sqrt{\pi}and describe its evolution.Homework Equations \Psi(x, t)=\int_{-\infty}^{\infty} a(k)e^{i\{kx-w(k)t\}}dkThe Attempt at a Solution know...
  20. B

    Integrating a function involved error functions and a Gaussian kernel

    I am currently facing a problem of integrating exp(-ax^2)*erf(bx+c)*erf(dx+f) with the integral boundaries 0 and infinity. I have gone through some handbooks but what I could locate is the integration of exp(-ax^2)*erf(bx)*erf(cx) from 0 to infinity which yields...
  21. H

    Finding a,b,c for Gaussian Model: A Puzzling Task

    If given a set of data points, how do I find a,b,c to input into a gaussian model? y = a exp (-(x-c) / b)2 I know it's centered at x=c Intersects at (0,a), but if the data doesn't have a "0", how do you find it? Also, a controls the height, but in what way? and b controls the spread, but in...
  22. J

    Gaussian basis set in DFT calculation

    I'm curious to know why chemists like to use Gaussian basis set in case of an ab-initio (ex.DFT) calculation. I understand that the molecules that are of interest to chemists are non-periodic and hence plane wave basis is not useful, but can't they use other real space basis like a grid? What...
  23. W

    Statistical Error of Centroid of Gaussian Distribution

    Statistical "Error" of Centroid of Gaussian Distribution If I have L data samples, distributed randomly (3D real Gaussian distibution, unity variance) about the origin in 3D real space, how can I derive an expression for the "origin estimation error" (i.e. the distance between the true origin...
  24. L

    What is the Gaussian Curvature of a Cone at its Vertex?

    Hi, I know that you can determine that the Gaussian curvature of a cone tends to infinity at the vertex, but seeing as the curvature anywhere else on the cone is zero, how is this possible?
  25. D

    1 Dimensional Representation of a Gaussian Distribution

    Hi, I currently have a Gaussian distribution (Normalized Frequency on the y-axis and a value we can just call x on the x-axis). So for the sake of simplicity, let's say that I ignore any values below 0 and any values above 1 on the x-axis. Then what I will do is take 10 equal segments...
  26. M

    Complex Error Functions as Solutions to Gaussian Integrals

    I have been told that the following integral can be expressed analytically as a combination of error functions of t. And that the solution can be obtained from then by numerically integrating over t. \int^a_b sin(k_1x)sin(k_2x')\int_0^\infty \frac{1}{\sqrt{t}}e^{-t(x-x')^2}dtdx dx' While...
  27. D

    Gaussian Distribution Problem.

    Hi, I currently have a Gaussian distribution (Normalized Frequency on the y-axis and a value we can just call x on the x-axis). So for the sake of simplicity, let's say that I ignore any values below 0 and any values above 1 on the x-axis. Then what I will do is take 10 equal segments...
  28. F

    Why Does Gaussian Integration Work?

    Hi all, why does Gaussian Integration in one dimension with n points integrate exactly with a polynomial of order 2n-1 ? thanks
  29. S

    Create Gaussian Function from Coords: Learn Integration & Matrix

    I am completely new to this so bare with me. I have co-ordinates and I want to create a Gaussian function. I already know the function which is y=0.01235140544*e^(-(x-36.28663863)^2/(-135.1643617)) But I need to know how to get a,b,c The Coordinates are {35,.01} {28,0.03} {20,.1} {15,.3}...
  30. C

    Second order differential nonhomogeneous equation with gaussian term

    Hello forum, I am trying to solve a differential equation for the last four hours and I can't figure out how... here it is \frac{d^2x(t)}{dt^2} + \frac{dx(t)}{dt} + c x(t) = d e^{-a t^2} actually my problem is how to handle the Gaussian term... if anyone can help please...
  31. T

    How Do Parabolas Relate to Gaussian Elimination?

    Got it
  32. A

    Calculate Expectation Value & SD of N1, N2 in 0.1m^3 Vacuum Chambers

    The conc.of molecules in two ultra-high-vacuum chambers of volumes V1=V2=0.1m^3 is 10^6 molecules/m3 You count the # of molecules N1 and N2, in each chamber at some moment of time. a.find the expectation value and the SD of N1 and N2 . calc \sigma_{N1}, sketch the prob distribution of N1...
  33. J

    Exponentially Modified Gaussian

    I am fitting a detector response using Matlab. I have been asked to fit the spectrum using a Exponentially Modified Gaussian. This is as follows. [ tex ] a^x_n [ /tex ] h(t) = [ tex ] \frac{A}{\sqrt{2 \pi} \sigma} e^{-\frac{(t-t_{R})^{2}}{2\sigma^{2}} [ /tex ] f(t) = [ tex ]...
  34. P

    Gaussian Modeling and Calculators

    I'm trying to figure out how to enter this into my calculator and get a graph, but I think it may be underpowered. I have a Casio fx-9860gii, to be clear. The problem is: y=0.0034e^-(x-515)/26,912 200 greater than/equal to x smaller than/equal to 800 Thanks for any assistance. :-)
  35. M

    Magnet with negative charge in gaussian surface?

    i would really appreciate if someone could help me out with this one. i m preparing for an exam and this question is a question from papers of previous years and its bugging me because it seems very specific in that i can't seem to find anything like it in textbooks. what i m mainly stuck on...
  36. M

    Magnet with negative charge in gaussian surface?

    i would really appreciate if someone could help me out with this one. i m preparing for an exam and this question is a question from papers of previous years and its bugging me because it seems very specific in that i can't seem to find anything like it in textbooks. what i m mainly stuck on...
  37. X

    Rearranging Two-Dimensional Gaussian Function.

    I'm not sure if this is the right place to post this. Let me say, this is not for any homework. I've been asking all over the internet with help for this, and no one seems to be able to know. I am applying this function to a Program I am writing in Delphi. I have no trouble applying it how it...
  38. matqkks

    Gaussian Elimination: Solving Systems of Linear Equations

    Is it correct that the Gaussian elimination procedure is used in computer software to solve systems of linear equations?
  39. F

    Area under Gaussian peak by easy measurements

    First I try to find a way of finding area under Gaussian peak by using simple means. Questions at bottom of post. This concerns peaks with Gaussian distribution, eg. peaks in a chromatogram in some chemical analysis. The Gaussian distribution is f(x) = \frac{1}{\sigma...
  40. A

    MATLAB [Matlab] FFT Gaussian x-space -> p-space scalings.

    Hi There, Im having a little trouble with scalings required for a fft performed in Matlab. So here is the story: I construct a position space gaussian, plot this guy out to 6 stdDev. My frontfactor is such that my probability density is normalized. I know what the actual Fourier transform...
  41. N

    Convolution of a gaussian function and a hole

    Hello, I want to do the convolution of a gaussian function and a hole. If I want to use Fourier transform which functions should I use? Can I use rms? I want to calculate the spot size of a gaussian signal after a circular aperture. Thanks!
  42. I

    Gaussian surfaces: Electric Field=zero

    Please explain to me in detail why a gaussian surface within a conductor has an electric field of zero? thanks.
  43. N

    Matlab Gaussian elimination with partial pivoting

    Homework Statement Hi all, I'm writing a program to solve a system of linear algebraic equations using the method of Gaussian elimination. The only thing I can't figure out is how to perform the actual pivot. In the %Forward elimination nest, I can't figure out how I am supposed to find the...
  44. G

    The Physics Behind Gaussian Guns

    I'm sorry this is not really a school question i was just intrigued and did not now where else to ask about it. I have seen videos of these Gaussian guns and they appear to generate energy from nowhere, obviously impossibly. So what is the physics behind how they work?
  45. M

    Gaussian Integration Error

    Hi, Im learning about gaussian integration right now but i can't really find anything about the error approximation other than that it goes proportional to the 2nth derivative of the function at some point in the interval I am trying to integration the function over. But that doesn't really...
  46. M

    MAP for multivariate gaussian?

    The standard multivariate gaussian is given by: http://upload.wikimedia.org/math/1/c/d/1cd250fc27ef7b7a9da469416333d07f.png taken from: http://en.wikipedia.org/wiki/Multivariate_normal_distribution The parameters can be estimated using...
  47. C

    Calculating Electric Flux Φ w/o typical Gaussian surface

    Hello all, new here. In the past few weeks, I have been trying to gain a basic understanding of classical electricity and magnetism through the fantastic lectures at http://ocw.mit.edu, specifically the physics course...
  48. M

    Converting a Gaussian Markov random field

    Hi I am currently reading: http://www.cs.cornell.edu/~asaxena/learningdepth/saxena_ijcv07_learningdepth.pdf which deals with reconstructing depth from a single still image. A gaussian multiscale markov random field is trained in a supervised context where the model is shown below...
  49. R

    Intensity & Amplitude of Gaussian Beam

    Can tell me the exact relationship between the intensity and the amplitude for a gaussian beam ? I know that I is proportional to |A|2 .. but i want the value of this proportianality constant
  50. A

    Gaussian frequency job after optimization

    Hi, I already got some good Gaussian-help in this forum, so maybe somebody can help me once again :) I did an optimization run for my structure in Gaussian and didn't know, that I could have combined this with a frequency calculation. So now I have to start a new frequency job based on my...
Back
Top