CRYSTAL Users Support

FAQs

> I have a question about the Fermi level. I wonder where the Fermi level
> should be placed in Crgra2003 ? The Fermi level is not placed on the
> top of the valence band. I am attaching the results obtained using DLV
> and the runcry03 script.

The usual definition of "Fermi level" is (Ashcroft Mermin, Solid State
Phsics) "energy below which the one-electron levels are occupied and
above which they are unoccupied in the groud state of a metal
". It does
not specify a unique energy in the case of a semiconductor: any energy
in the gap separates occupied from unoccupied levels at T=0"

Following this definition, Crgra2003 choice is -not- to draw Fermi level
for insulator and semiconductors.
DLV choice is to draw a Fermi level on top of occupied bands.

 

> Gaussian 98 - CRYSTAL03 energy
> If I run Gaussian 98 using the input generated by CRYSTAL03 with the keyword
> GAUSS98 I do not obtain the same energy. What is the problem?
>

There are 3 main differences between a standard CRYSTAL run and a GAUSSIAN run.

1. CRYSTAL adopts by default bypolar expansion to compute coulomb integrals when the two 
    distributions do not overlap. 
    Insert keyword NOBIPOLA to compute all 2 electron integrals exactly; 

2. CRYSTAL adopts a basis set with 5D and 7F AO; 

3. CRYSTAL adopts the NIST conversion factor bohr/Angstrom CODATA98. 
     Insert the keyword BOHRANGS, followed by the conversion factor adopted by Gaussian

Example: neopenthane

 

 

 

Bug Fixing Information

 

Errata

  • CRYSTAL User's Manual Errata
  • CRYSTAL Tutorials Errata