<html xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"> <head> <meta http-equiv="Content-Type" content="text/html; charset=Windows-1252"> <meta name="Generator" content="Microsoft Word 15 (filtered medium)"> <style></style> </head> <body lang="en-CH" link="blue" vlink="purple" style="word-wrap:break-word"> <div class="WordSection1"> Hi<o:p></o:p> <o:p> </o:p> CP2K handles all quantities internally in atomic units [a.u.]. You can use the conversion factors printed in the top of the CP2K output for the conversion:<o:p></o:p> <o:p> </o:p> [a.u.] -> [fs] 2.41888432650478E-02<o:p></o:p> [a.u.] -> [K] 3.15774647902944E+05<o:p></o:p> <o:p> </o:p> The formula for the barostat mass is<o:p></o:p> <o:p> </o:p> M(barostat) = (N(dof) + d)*T*tau^2 (with tau = 1/omega) <o:p></o:p> <o:p> </o:p> d = 3 (dimensional system)<o:p></o:p> N(dof) = 3*N(atom) – 3 = 3*64 - 3<o:p></o:p> T = 1200 K / 3.15774647902944E+05 [K/a.u.]<o:p></o:p> tau = 50 fs / 2.41888432650478E-02 [fs/a.u.]<o:p></o:p> <o:p> </o:p> M(barostat) = (3*64 – 3 + 3)*(1200.0/3.15774647902944E+05)*(50.0/2.41888432650478E-02)**2 = 3117561.45265 a.u.<o:p></o:p> <o:p> </o:p> With periodic boundary conditions (PBC), the degrees of freedom (dof) have to be reduced by 3 (translational dof).<o:p></o:p> You can ignore k (Boltzmann) when using atomic units.<o:p></o:p> <o:p> </o:p> HTH<o:p></o:p> <o:p> </o:p> Matthias<o:p></o:p> <o:p> </o:p> <div id="mail-editor-reference-message-container"> <div> <div> <div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm"> From: cp2k@googlegroups.com <cp2k@googlegroups.com> on behalf of Michela Benazzi <bnzmichela@gmail.com> Date: Tuesday, 27 August 2024 at 15:09 To: cp2k <cp2k@googlegroups.com> Subject: [CP2K:20624] Barostat/Thermostat mass units?<o:p></o:p> </div> <div> Hello CP2K users,<o:p></o:p> </div> <div> I have previously asked a question about what kind of barostat CP2K uses, and Thomas Kuhne linked a paper on MTTK barostat which was very helpful (https://aiichironakano.github.io/phys516/Martyna-Integrator-MolPhys96.pdf).<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> However, I tried to calculate my barostat mass to understand the units and I am still at a loss - currently, my restart BAROSTAT MASS is 3.1175614526535734E+006. According to the CP2K manual, the units could be kg, m_e or amu. I tried to calculate it myself following the MTTK formula and there is no match: W = (N_f + 9)* (k_b*T)/2 * (t_p/2pi)^2<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> where t_p is the time constant (50 fs), T = 1200 K and N_f is degrees of freedom (aka number of atoms? 64 in my system).<o:p></o:p> </div> <div> <o:p> </o:p> </div> <div> My result is 6.0124759e-47 J (kg*m2), which is in units of moment of inertia. Even if I convert it to m_e or amu it does not match: 6.0124759e-47 J (kg*m2) <o:p></o:p> (or 3.61328477e+27 amu*m2)<o:p></o:p> (or 6.60031109024e-17 m_e*m2)<o:p></o:p> <o:p> </o:p> I was wondering if:<o:p></o:p> <o:p> </o:p> 1) there are other units I have not considered in CP2K, or if CP2K internally converts to something else.<o:p></o:p> 2) Degrees of freedom =/= number of atoms?<o:p></o:p> 3) I am supposed to get rid of the m2 term by dividing by area in some way, although I am not sure how scientifically sound it would be, since we have a 3D unit cell.<o:p></o:p> <o:p> </o:p> Thank you very much!<o:p></o:p> </div> -- You received this message because you are subscribed to the Google Groups "cp2k" group. To unsubscribe from this group and stop receiving emails from it, send an email to <a href="mailto:cp2k+unsubscribe@googlegroups.com">cp2k+unsubscribe@googlegroups.com</a>. To view this discussion on the web visit <a href="https://groups.google.com/d/msgid/cp2k/a7e5ea36-12ae-495e-adb3-f0e5d2b14a28n%40googlegroups.com?utm_medium=email&utm_source=footer"> https://groups.google.com/d/msgid/cp2k/a7e5ea36-12ae-495e-adb3-f0e5d2b14a28n%40googlegroups.com</a>.<o:p></o:p> </div> </div> </div> </div> </body> </html> -- You received this message because you are subscribed to the Google Groups "cp2k" group. To unsubscribe from this group and stop receiving emails from it, send an email to <a href="mailto:cp2k+unsubscribe@googlegroups.com">cp2k+unsubscribe@googlegroups.com</a>. To view this discussion on the web visit <a href="https://groups.google.com/d/msgid/cp2k/ZRAP278MB0827DDBF85A8840E7B7CC618F4942%40ZRAP278MB0827.CHEP278.PROD.OUTLOOK.COM?utm_medium=email&utm_source=footer">https://groups.google.com/d/msgid/cp2k/ZRAP278MB0827DDBF85A8840E7B7CC618F4942%40ZRAP278MB0827.CHEP278.PROD.OUTLOOK.COM</a>.