Dear QE friends and Paolo, I’m sorry to break into this mail thread, but could you elaborate a bit on “applying acoustic sum rule”.
How is this done? Met vriendelijke groeten, Mit freundlichen Grüßen, With kind regards, Willem Offermans Researcher Electrocatalysis SCT VITO NV | Boeretang 200 | 2400 Mol Phone:+32(0)14335263 Mobile:+32(0)492182073 [email protected]<mailto:[email protected]> [cid:[email protected]] On 14 Sep 2020, at 08:34, Paolo Giannozzi <[email protected]<mailto:[email protected]>> wrote: Apparently the largest discrepancies come from low-energy modes, in particular zero-frequency acoustic modes (those with "negative" frequencies that become zero when acoustic sum rule is applied). Even minor changes in the way exchange-correlation is computed may lead to surprisingly large but unphysical differences for those modes. Paolo On Sun, Sep 13, 2020 at 7:54 PM Unmesh Mondal <[email protected]<mailto:[email protected]>> wrote: Dear all, I intend to calculate the vibrational modes of gas phase HCOOH (formic acid) molecule. The "ph.x" vibrational frequencies (in cm-1) of the system for the two versions of quantum espresso (6.5 and 6.4 : with same compilers) are: (QE 6.5) (QE 6.4) 1 -207.654081 -207.686563 2 -63.775769 -61.840758 3 -55.090067 -57.158594 4 -15.183543 -15.903109 5 20.311666 21.386665 6 129.683418 129.214185 7 615.352300 615.209434 8 676.597853 676.547298 9 999.285772 999.331118 10 1071.840671 1071.779138 11 1253.496419 1253.514267 12 1350.618940 1350.925730 13 1735.698557 1735.582574 14 2965.285270 2965.885980 15 3665.961548 3665.948232 The maximum difference in any frequency for the two versions is about 2 cm-1. My question: Is the difference of 2 cm-1 within the error limit of ph.x calculations? What is the accuracy we expect in reporting the vibrational frequency (via ph.x)? Regards and Thanks Unmesh Mondal IISER Pune, India _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso<https://eur02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.max-centre.eu%2Fquantum-espresso&data=02%7C01%7C%7Ceb09c593764540a31b7d08d858786b5c%7C9e2777ed82374ab992782c144d6f6da3%7C0%7C0%7C637356621508435090&sdata=kTKqeX%2F%2F%2BO6kPNwef4FIkRfJEGe0%2F%2BN3PfxwhTEI0vM%3D&reserved=0>) users mailing list [email protected]<mailto:[email protected]> https://lists.quantum-espresso.org/mailman/listinfo/users<https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.quantum-espresso.org%2Fmailman%2Flistinfo%2Fusers&data=02%7C01%7C%7Ceb09c593764540a31b7d08d858786b5c%7C9e2777ed82374ab992782c144d6f6da3%7C0%7C0%7C637356621508445049&sdata=3H9VxidE80u1fJGpErn5ia73gcU1wHWEO%2BBKUGsKTEo%3D&reserved=0> -- Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222 _______________________________________________ Quantum ESPRESSO is supported by MaX (https://eur02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.max-centre.eu%2Fquantum-espresso&data=02%7C01%7C%7Ceb09c593764540a31b7d08d858786b5c%7C9e2777ed82374ab992782c144d6f6da3%7C0%7C0%7C637356621508464957&sdata=Ve%2ByVOhyxj96wsoUv84X01T7RhUF%2BsbovgeiBIRDERA%3D&reserved=0) users mailing list [email protected]<mailto:[email protected]> https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.quantum-espresso.org%2Fmailman%2Flistinfo%2Fusers&data=02%7C01%7C%7Ceb09c593764540a31b7d08d858786b5c%7C9e2777ed82374ab992782c144d6f6da3%7C0%7C0%7C637356621508464957&sdata=35lAnSluB8%2BFUxrP7RLiFDVqfOKa7Qs7Xi94ZtlXEq0%3D&reserved=0 VITO Disclaimer: http://www.vito.be/e-maildisclaimer
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