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MolCToy Detailed Description

(Molecular Conduction: Toy Models)

The four programs run from this page are simple theoretical models of the conduction through individual molecules in between two contacts. Although simple, they illustrate most of the phenomena found in more advanced models.

The models are:

1. One level model (only one molecular orbital included)
2. The same as model 1, but including broadening of the molecular orbital by the contacts
3. The same as model 2, but considering unrestricted solutions (i.e. the spin up and down states are treated separately)
4. The same as model 1, except for two levels

These four models are described in more detail in section 3 of "Theory of Molecular Conduction".

The parameters needed by the models are:

1. The Fermi energy of the contacts (Ef)
2. The energy of the molecular level(s) responsible for the conduction (E0,E1)
3. The broadening (interaction strength) between the molecular level and the two contacts (Gamma1, Gamma2)
4. The charging energy (U0) (i.e. How much does the energy level shift when the molecule becomes charged?)
5. The temperature (T)

Interesting cases to try:

• How does the charging energy affect the I-V? Try U0=0 eV, U0=1 eV!
• Can we obtain asymmetric I-V? Try Gamma1=0.2, Gamma2=0.05!
• Coulomb Blockade? Try Gamma1=Gamma2=0.05, U0=1.0!
• Does the temperature really change anything?