MChem Master of Chemistry Computational Chemistry 1

Question 1

Which method uses the Born-Oppenheimer approximation to separate nuclear and electronic motion?

Accepted Answer

Ab initio quantum chemistry

Answer

Ab initio quantum chemistry relies on the Born-Oppenheimer approximation to treat nuclear and electronic degrees of freedom separately.

Question 2

In density functional theory (DFT), the exchange-correlation functional approximates which quantity?

Accepted Answer

Many-body exchange and correlation effects

Answer

The exchange-correlation functional in DFT approximates the complex many-body exchange and correlation effects that cannot be computed exactly.

Question 3

What is the primary advantage of the B3LYP hybrid functional in DFT calculations?

Accepted Answer

It combines exact Hartree-Fock exchange with DFT correlation for improved accuracy

Answer

B3LYP mixes a portion of exact HF exchange with DFT exchange and correlation functionals, yielding improved thermochemical accuracy.

Question 4

In molecular dynamics (MD) simulations, what does the NPT ensemble maintain constant?

Accepted Answer

Number of particles, pressure, and temperature

Answer

The NPT (isothermal-isobaric) ensemble keeps the number of particles (N), pressure (P), and temperature (T) constant.

Question 5

Which basis set type uses Slater-type orbitals approximated by Gaussian functions?

Accepted Answer

Pople-style split-valence basis sets (e.g., 6-31G)

Answer

Pople-style basis sets like 6-31G approximate Slater-type atomic orbitals using contracted Gaussian functions for computational efficiency.

MChem Master of Chemistry Practice Test