Electron Correlation and Methods Past Hartree-Fock · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

What Hartree-Fock leaves out

Science · Chemistry · ages 23-24
Name ______________________   Date ____________

  1. What is the correlation energy?

    • The energy of a light beam
    • The heat of the laboratory
    • The energy lost by averaging over the electrons

  2. What does Hartree-Fock miss?

    • Electrons dodging each other moment by moment
    • The nuclei entirely
    • The number of electrons present

  3. Coupled cluster costs far more than perturbation theory as molecules grow.

    Circle one:   True   False

  4. Why does a breaking bond need different treatment?

    • Two arrangements compete and no single picture rules
    • Bonds never break inside calculations
    • Electrons move faster when stretched

  5. Which ranking of accuracy is right?

    • Both methods are exactly exact
    • Coupled cluster beats perturbation
    • Perturbation beats coupled cluster

  6. A large molecule at equilibrium and a small computer: what do you choose?

    • Nothing can be computed at all
    • Waiting years for a bigger machine
    • Perturbation, accepting wider error bars

  7. A small molecule at equilibrium and cost is no object: what do you choose?

    • Coupled cluster, keeping a small stated error
    • No method at all
    • Perturbation to save money

  8. A student runs a standard single-picture method on a breaking bond. What is wrong?

    • Nothing is wrong: one picture fits all bonds
    • The method assumes one arrangement dominates, which fails here
    • Breaking bonds need less care, not more
LightMySky · lightmysky.comW1-mt_3F5B8V7CGb-s1

Answer key

For grown-ups. Fold this page away before handing over the rest.

What Hartree-Fock leaves out W1-mt_3F5B8V7CGb-s1

  1. The energy lost by averaging over the electrons · It is defined by the approximation it corrects. Averaging defines it.
  2. Electrons dodging each other moment by moment · Averaging erases the dodging. The missing motion is the gap.
  3. True · Fuller corrections climb faster. Cheap stays cheap.
  4. Two arrangements compete and no single picture rules · One dominant picture is gone. Tools assuming it mislead.
  5. Coupled cluster beats perturbation · Fuller correction wins on accuracy. Cheap and rough trails.
  6. Perturbation, accepting wider error bars · Fit the method to the machine. State the error you keep.
  7. Coupled cluster, keeping a small stated error · Spend for accuracy where it fits. Even then, name the leftover error.
  8. The method assumes one arrangement dominates, which fails here · The tool assumes a winner. A tie breaks the assumption.
Worksheet · LightMySky