<div dir="ltr"><p class="MsoNormal" style="line-height: normal;"><span style="font-size: 10pt; font-family: Arial, sans-serif; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial;">Dear
cp2k users and developers,</span><span style="font-size:12.0pt;font-family:
"Times New Roman",serif;mso-fareast-font-family:"Times New Roman""><o:p></o:p></span></p>

<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial;"><span style="font-size: 10pt; font-family: Arial, sans-serif;"> </span></p>

<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial;"><span style="font-size: 10pt; font-family: Arial, sans-serif;">I am testing a NVE
simulation with velocity scaling for crystalline CaO (300 K) and having
questions regarding the drift of center of mass.<o:p></o:p></span></p>

<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial;"><span style="font-size: 10pt; font-family: Arial, sans-serif;"> </span></p>

<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial;"><span style="font-size: 10pt; font-family: Arial, sans-serif;">In a regular NVE
simulation, I am expecting that (1) the simulation box is fixed and positions
of atoms can be in fractional/scaled or Cartesian units, (2) if atoms moved out
of the simulation box, they can be folded back to the box or left unchanged,
(3) the mass-averaged position centers oscillate around x, y, z direction.  I am showing the center of mass positions
from VASP, which are consistent with the expectation.<o:p></o:p></span></p><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial;"><span style="font-size: 10pt; font-family: Arial, sans-serif;"><br></span></p><p class="separator" style="text-align: center; clear: both;"></p><p class="separator" style="text-align: center; clear: both;"><a imageanchor="1" href="https://lh3.googleusercontent.com/-tRDdhXVYalE/WGxP2ScXNBI/AAAAAAAAhnk/8bGLtoxRwxINxHoXywkIJFBPOkR4IipMwCLcB/s1600/cp2k-vs-VASP.TIF" style="margin-left: 1em; margin-right: 1em;"><img src="https://lh3.googleusercontent.com/-tRDdhXVYalE/WGxP2ScXNBI/AAAAAAAAhnk/8bGLtoxRwxINxHoXywkIJFBPOkR4IipMwCLcB/s400/cp2k-vs-VASP.TIF" border="0" width="400" height="170"></a></p><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial;"><span style="font-size: 10pt; font-family: Arial, sans-serif;"><br></span></p><p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial;"><span style="font-size: 10pt; font-family: Arial, sans-serif;"><br></span></p>

<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial;"><span style="font-size: 10pt; font-family: Arial, sans-serif;"> </span></p>

<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial;"><span style="font-size: 10pt; font-family: Arial, sans-serif;">If I do the same for
cp2k (input file enclosed), I am clearly seeing drift of center of mass.  If I analyze the dynamics of the trajectory
(now shown), it appears that both Ca and O atoms are diffusing instead of
vibrating, as obtained from VASP trajectory.<o:p></o:p></span></p>

<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial;"><span style="font-size: 10pt; font-family: Arial, sans-serif;"> </span></p>

<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial;"><span style="font-size: 10pt; font-family: Arial, sans-serif;">I am wondering if you
have seen similar behaviors or if I have the wrong settings in the input file.<o:p></o:p></span></p>

<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial;"><span style="font-size: 10pt; font-family: Arial, sans-serif;"> </span></p>

<p class="MsoNormal" style="margin-bottom: 0.0001pt; line-height: normal; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial;"><span style="font-size: 10pt; font-family: Arial, sans-serif;">Thanks, Wei<o:p></o:p></span></p></div>