[QE-users] E-field units inconsistent

[Stefano Baroni]

In anything, there may be discrepancies in the cp.x code, which uses Hartree a.u. (e=1 in those units). SB

On 15 Feb 2023, at 09:45, Lorenzo Bastonero <lbastone at uni-bremen.de> wrote:

Dear Joseph,

In Ry a.u. the electric charge is sqrt(2), thus the units are correct.

Best,
Lorenzo

********************************
Lorenzo Bastonero

PhD Student
U Bremen Excellence Chair,
Bremen Center for Computational Materials Science,
and MAPEX Center for Materials and Processes

University of Bremen
Faculty of Production Engineering
TAB-Building, Room 3.32
Am Fallturm 1
28359 Bremen, DE

http://www.hmi.uni-bremen.de/

Il giorno 14 feb 2023, alle ore 23:43, Joseph Frimpong <gy1906 at wayne.edu<mailto:gy1906 at wayne.edu>> ha scritto:

Dear Users and Developers,

I need clarifications on the finite e-field conversion factor for 1 a.u found on the input file description at https://www.quantum-espresso.org/Doc/INPUT_PW.html<https://www.quantum-espresso.org/Doc/INPUT_PW.html#idm840> and in the source code at $QEDIR/PW/src/extfield.f90.



Reading the input file description online: under “efield”, says in Ry a.u.; 1 a.u. = 36.3609*10^10 V/m



We know E-field in a.u. is 5.14220674763(78)×10^11 V⋅m−1 from https://en.wikipedia.org/wiki/Hartree_atomic_units; which means in Ry a.u., it should be 51.422/2 = 25.711, but the 36.3609 is actually 51.422/sqrt(2).



In the source code: $QEDIR/PW/src/extfield.f90, line #38, in the variable “eamp”, the comment says “(1 a.u. = 51.44 10^11 V/m)” which matches the Wikipedia result but not the INPUT_PW webpage.


Which one is correct?  Can someone please resolve this confusion?



Thanks for your time.

-----------------------------------------
Joseph Frimpong
Graduate Research Assistant
Department of Chemistry
Wayne State University


-----------------------------------------
Joseph Frimpong
Graduate Research Assistant
Liu's Group
Department of Chemistry
Wayne State University
5101 Cass Ave, Detroit, MI 48202
Phone: (313) 577-0552
https://liugroupwsu.weebly.com/
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_______________________________________________
The Quantum ESPRESSO community stands by the Ukrainian
people and expresses its concerns about the devastating
effects that the Russian military offensive has on their
country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
users mailing list users at lists.quantum-espresso.org
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—
Stefano Baroni - Trieste —  http://stefano.baroni.me




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