Questions tagged [ab-initio]
For questions relating to quantum chemistry using wavefunction-based methods and solving the Schrödinger equation.
45 questions
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I failed to make Claus benzene. (With sticks.)
Claus benzene must be the nonplusultra of deformation stress. Every time I get a chemistry toolkit in my hand, I try to make it. But even with sturdy tetrahedral "stop tacks" and solid ...
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How to straighforwardly access coefficients for writing molecular Hamiltonians?
I am a computational physicist working on a method that can also be used in spectroscopy. Using systems that I understand, such as Hénon-Heiles, Fermi-Pasta-Ulam-Tsingou chains or coupled Morse ...
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Ab initio calculation of optical line strengths
30 years ago, I made my Ph.D. (mostly) by fitting crystal field parameters (read: radial integrals) to observed transitions in the optical spectra of lanthanid compounds (mostly organometallics, with ...
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Critical point from ab initio calculations
I was wondering if it is possible to calculate the critical point (e.g., temperature, pressure, and density) other than via experiments or equations of state like ab initio calculations.
Would anyone ...
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Are there examples of publications using DFT instead of HF as a coupled-cluster reference?
Are there examples of publications using DFT instead of HF as a coupled-cluster reference?
I have been searching for a while, and only managed to find an article by M. Saitow,[1] where CAM-B3LYP ...
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Need for AINR-based simulations (vs. laboratory experimentation)
The Results section of this paper related to ab initio molecular dynamics states that "16 $\ce{H_2O}$ and 15 $\ce{HCN}$ molecules were taken together, and the system was allowed to evolve for 750 ...
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Resource estimate for ab initio calculation [closed]
I have recently come across this very intriguing paper “The Fundamental Vibration of Molecular Hydrogen”.
I have asked the authors the following naïve questions directly via email?
What was the ...
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Effective core potential and Gaussian basis set
Is using the effective core potential (ECP) and Gaussian basis set simultaneously in ab initio calculation a valid approach? For example, is it correct to use ECP for one of the atoms and, instead of ...
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Potential energy surface in transition state theory
I would like to study the typical reaction from the transition state theory:
$$\ce{AB + C <=> ABC^‡ -> A + BC}$$
Assuming $\ce{ABC^‡}$ is a colinear molecule, the potential energy surface of ...
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Is the Hartree-Fock determinant always the minimum energy single Slater determinant solution to a molecular Hamiltonian?
Is it always true that the Hartree-Fock slater determinant is the minimum energy single slater determinant solution to a given molecular Hamiltonian $H$?
By construction, any determinant $|\chi_{i_1}\...
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How to plot the wave function after a Hartree-Fock calculation?
I have written a code in Mathematica and have obtained the final energy of the hydrogen molecule. I have used Gaussian basis functions for this calculation. Now I need to plot the ground state wave ...
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Ab initio method to calculate C-C bond dissociation energy?
I'm trying to review how to calculate bond dissociation energy for C-C in ethane, a very simple calculation (or should be).
I get the following Hartree energies for SCF 6-31G(p) for methane, ethane, ...
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Is there a rule of thumb to predict when coupled cluster might dip below the variational limit?
Coupled cluster is a non-variational method, meaning that it can give energies that are below the true FCI energy (the "variational limit" for variational methods).
Often coupled cluster ...
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What are the steps of Hartree-Fock Theory?
Outline the steps involved in the Hartree–Fock method for the calculation of molecular electronic structure.
I understand the basics of HF, in that it does not account for electron correlation (...
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Calculating the Molecular Orbitals of a Molecular State [closed]
I am performing ab initio calculations on a heteronuclear diatomic compound using the MRCI method on the MOLPRO quantum chemistry package. I obtained the molecular states of the compound but I was ...
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