Dear David, the value of a is definitely in Angstrom ( https://www.quantum-espresso.org/Doc/INPUT_PW.html#idm258). If with 12 A it works and with 6 A it does not work, this means that maybe your unit cell with 6 A side is not able to accommodate the atoms (this could be inferred only if you provided the whole input).
Let me also point out that, as far as the CELL_PARAMETERS card is concerned, you should (maybe) find in the output (at the beginning) a message saying that it has been ignored. Indeed, if you DO specify ibrav >0, the unit cell vectors are chosen by the code with the parameters given in input ( https://www.quantum-espresso.org/Doc/INPUT_PW.html#idm224), whereas the input from the CELL_PARAMETERS ard is allowed only with ibrav = 0. Generally speaking, it is worth visualizing the input (using for example XCrysDen able to directly open QE input files) before attempting any calculation. Giovanni -- Giovanni Cantele, PhD CNR-SPIN c/o Dipartimento di Fisica Universita' di Napoli "Federico II" Complesso Universitario M. S. Angelo - Ed. 6 Via Cintia, I-80126, Napoli, Italy e-mail: [email protected] <[email protected]> Phone: +39 081 676910 Skype contact: giocan74 ResearcherID: http://www.researcherid.com/rid/A-1951-2009 Web page: https://sites.google.com/view/giovanni-cantele/home Il giorno sab 8 lug 2023 alle ore 13:28 <[email protected]> ha scritto: > Dear all, > > I'm starting to study a perovskite and I am a bit confused about the > parameter "a" of the SYSTEM card. > > According to the pw.x input page of QE this parameter must be in > angstroms. I have a calculation in which, apparently, this parameter > is in bohr: > > &SYSTEM > ibrav = 2 > a = 12.1616 > > With these numbers, the calculation starts and finshes well. > > I have done the simple check of changing "a" to 6.0808. This last > value should be angstroms and it should work, according to the webpage: > > &SYSTEM > ibrav = 2 > a = 6.0808 > > But, this new calculation does not finish and blows up just after > starting. > > For both of them, I have used: > > CELL_PARAMETERS angstrom > 6.08 -4.10 0.00 > 6.08 -4.10 0.00 > -0.46 0.00 31.37 > > ... > > ATOMIC_POSITIONS crystal > Pb 0.45 0.06 0.04 > Pb 0.06 0.45 0.54 > > ... > > > I don't know what is going on. The parameter "a" is in bohr or in > angstroms? > > Thanks for your help, David. > > > > -------------------------- > David López Durán > Department of Physics > University of Córdoba, Spain > Phone: +34 957 21 20 32 > https://es.linkedin.com/in/davidlopezduran > > _______________________________________________ > 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 [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users >
_______________________________________________ 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 [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
