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
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