<div dir="ltr"><div>Dear Professor Hutter and your group members, </div><div><br></div>I checked the source code, and found IR intensity is equal to <span style="color:rgb(0,0,0);font-family:Menlo;font-size:12px;font-variant-ligatures:no-common-ligatures;background-color:rgb(252,248,255)">SQRT(DOT_PRODUCT(D_deriv, D_deriv)). Based on Darling and Schlegel's paper, the IR intensity is proportional to (d(mu)/dQ)^2. So does it mean the IR intensity should be </span><span style="color:rgb(0,0,0);font-family:Menlo;font-size:12px;font-variant-ligatures:no-common-ligatures;background-color:rgb(252,248,255)">DOT_PRODUCT(D_deriv, D_deriv), not </span><span style="color:rgb(0,0,0);font-family:Menlo;font-size:12px;font-variant-ligatures:no-common-ligatures;background-color:rgb(252,248,255)">SQRT(DOT_PRODUCT(D_deriv, D_deriv))? (Is this a mistake??)</span><div><br></div><div>Here I attach Darling and Schlegel's paper. </div><div><br></div><div>The source code is <span style="font-variant-ligatures:no-common-ligatures;background-color:rgb(252,248,255);color:rgb(0,0,0);font-family:Menlo;font-size:12px">vibrational_analysis.F, </span></div><div><span style="font-variant-ligatures:no-common-ligatures;background-color:rgb(252,248,255);color:rgb(0,0,0);font-family:Menlo;font-size:12px"><br></span></div><div>
<p class="gmail-p1" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:12px;line-height:normal;font-family:Menlo;color:rgb(0,0,0);background-color:rgb(252,248,255)"><span class="gmail-s1" style="font-variant-ligatures:no-common-ligatures"><span class="gmail-Apple-converted-space"> </span>IF (calc_intens) THEN</span></p>
<p class="gmail-p1" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:12px;line-height:normal;font-family:Menlo;color:rgb(0,0,0);background-color:rgb(252,248,255)"><span class="gmail-s1" style="font-variant-ligatures:no-common-ligatures"><span class="gmail-Apple-converted-space"> </span>D_deriv = 0._dp</span></p>
<p class="gmail-p1" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:12px;line-height:normal;font-family:Menlo;color:rgb(0,0,0);background-color:rgb(252,248,255)"><span class="gmail-s1" style="font-variant-ligatures:no-common-ligatures"><span class="gmail-Apple-converted-space"> </span>DO j = 1, nvib</span></p>
<p class="gmail-p1" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:12px;line-height:normal;font-family:Menlo;color:rgb(0,0,0);background-color:rgb(252,248,255)"><span class="gmail-s1" style="font-variant-ligatures:no-common-ligatures"><span class="gmail-Apple-converted-space"> </span>D_deriv(:) = D_deriv(:) + dip_deriv(:, j)*Hint2(j, i)</span></p>
<p class="gmail-p1" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:12px;line-height:normal;font-family:Menlo;color:rgb(0,0,0);background-color:rgb(252,248,255)"><span class="gmail-s1" style="font-variant-ligatures:no-common-ligatures"><span class="gmail-Apple-converted-space"> </span>END DO</span></p>
<p class="gmail-p1" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:12px;line-height:normal;font-family:Menlo;color:rgb(0,0,0);background-color:rgb(252,248,255)"><span class="gmail-s1" style="font-variant-ligatures:no-common-ligatures"><span class="gmail-Apple-converted-space"> </span>intensities(i) = SQRT(DOT_PRODUCT(D_deriv, D_deriv))</span></p>
<p class="gmail-p1" style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:12px;line-height:normal;font-family:Menlo;color:rgb(0,0,0);background-color:rgb(252,248,255)"><span class="gmail-s1" style="font-variant-ligatures:no-common-ligatures"><span class="gmail-Apple-converted-space"> </span>END IF</span></p></div>
<div><br></div><div>Thanks ahead for your help, and Merry Christmas!!</div><div><br></div><div>Fangyong</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Dec 21, 2021 at 5:19 PM <a href="mailto:fyya...@gmail.com">fyya...@gmail.com</a> <<a href="mailto:fyyan2019@gmail.com">fyyan2019@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi, all,<div><br></div><div>What is the unit for IR intensity using normal mode analysis in cp2k? The IR intensity is proportional to d(mu) / dQ, d(mu) is the change of the dipole moment, and dQ is the change of normal mode coordinate Q. </div><div><br></div><div>There are prefactor for the exact IR intensity, see eq. 8 in Cynthia L. Darling and H. Bernhard Schlegel, J. Phys. Chem. 1994, 98, 5855-5861. </div><div><br></div><div>So what is the equation for calculating the IR intensity in cp2k, is there a reference for it? Once we know the equation, we can know the unit. </div><div><br></div><div>Thanks!</div><div><br></div><div>Fangyong</div>
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