A topological insulator thin film in an electric field

[paulfons]

Dear VASP users & developers,

I'm wondering if VASP 5.2.2 can simulate a topological insulator thin film in
a finite electric field. The structure is a slab calculation which is bulk in for an
infinite (periodic) system, but has surface bands with a linear dispersion (so-called
Dirac Cone like dispersion. I tried to simulate a Sb2Te3 slab in an
electric field Ez = 0.0005 eV/angstrom , but VASP issued the error messages listed below.

> CHECK_OCCUPATIONS: ERROR, system is not insulating.

> ;

> | One or more components of EFIELD_PEAD is too large for comfort, in all |

> | probability you are too near to the onset of Zener tunneling. |

> | |

> | e |E dot A_1| = 0.00000 > 1/10 E_g/N_1 = -0.00975 |

> | e |E dot A_2| = 0.00000 > 1/10 E_g/N_2 = -0.00975 |

> | e |E dot A_3| = 0.03960 > 1/10 E_g/N_3 = -0.04387 |

.

This sounds quite strange, because Eg has a negative value

-0.04387 * 10 * N_3 = -.87740 [eV],

and an electric field perpendicular to the surface of topological insulator film

cannot cause any current or any tunneling event.



Is it possible for the current VASP release (5.2.2) to simulate a toplogical

insulator thin film in an electric field, even when the field is small and its direction

is perpendicular to the film surface ?



with my best regards,

[support_vasp]

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