Hi, Jessica > 2021/03/30 1:53、Jessica Johnson <[email protected]>のメール: > > I have a very general question about Raman calculations (I will include that > I am using QE version 6.4.1 per the posting guidelines in case that helps my > answer my question).
The derivatives of the potential give the T^2 and T^3 dependencies for the Raman spectrum. To evaluate the quantities there may be two strategies. 1) Calculate the dynamics at the specified temperature using the Car–Parrinello MD or the BO-MD and evaluate the specified Raman mode. The temperature dependencies of the mode, such as the shift and the width, are the direct results of the anharmonic effects. 2) Evaluate the potential by slightly displacing the atoms following the Raman mode. The polynomial fit to the obtained potential curvature will give the third and forth derivatives and you may be able to evaluate the anharmonicities. I found the following ref. and hope it gives you a helpful hint. "Lattice dynamics of anharmonic solids from first principles" O. Hellman, I. A. Abrikosov, and S. I. Simak Phys. Rev. B 84, 180301(R) – Published 14 November 2011 best regards kazume NISHIDATE 敬具 西館数芽 [email protected] [email protected] _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
