Density Functional Theory and Choosing a Functional · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Density instead of wavefunction

Science · Chemistry · ages 20-21
Name ______________________   Date ____________

  1. What does the exchange-correlation functional account for?

    • The lab electricity bill
    • Part of the electron energy that must be approximated
    • The number of atoms

  2. Why work with the density at all?

    • It is a smaller object than the full wavefunction
    • It removes all electrons
    • It makes molecules heavier

  3. What distinguishes functional families?

    • Their color schemes
    • Their authors birthdays
    • Their accuracy and cost, and what each suits

  4. A stacking interaction reads as barely bound. What is the likely cause?

    • Too many atoms
    • A functional missing dispersion attraction
    • A broken hard drive

  5. You need decent molecular energies on a budget. Which rung do you try?

    • No functional at all
    • A random number generator
    • A hybrid, mixing exact exchange at higher cost

  6. The exact exchange-correlation functional is known and used everywhere.

    Circle one:   True   False

  7. A pricier functional always beats a cheaper one for every property.

    Circle one:   True   False

  8. Stacking reads as barely bound. What do you propose?

    • Delete one ring
    • Add a dispersion correction and recompute
    • Double the temperature
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Answer key

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

Density instead of wavefunction W1-mt_mmuzLeA62V-s1

  1. Part of the electron energy that must be approximated · Its exact form is unknown, so approximations stand in.
  2. It is a smaller object than the full wavefunction · One value per point in space scales far better.
  3. Their accuracy and cost, and what each suits · Families trade care against compute, fitting different jobs.
  4. A functional missing dispersion attraction · Common functionals underbind stacked rings without correction.
  5. A hybrid, mixing exact exchange at higher cost · Hybrids usually repay their price for molecules.
  6. False · It is unknown, which is why approximations exist.
  7. False · Families suit different jobs, so match the tool to the task.
  8. Add a dispersion correction and recompute · The correction restores the missing attraction between the rings.
Worksheet · LightMySky