<br><div id="yMail_cursorElementTracker_0.42352259857563834">Dear QE user,</div><div id="yMail_cursorElementTracker_0.42352259857563834"><br></div><div id="yMail_cursorElementTracker_0.42352259857563834">Must the vacuum created along the z-axis always be sandwich around the slab (eg 8Angstrom vacuum + slab + 8Angstrom vacuum if we want to use a 16A vacuum for a calculation) for all calculations involving surface properties?</div><div id="yMail_cursorElementTracker_0.42352259857563834"><br></div><div id="yMail_cursorElementTracker_0.42352259857563834"><br></div><div id="yMail_cursorElementTracker_0.42352259857563834">Thank you.</div><div id="yMail_cursorElementTracker_0.42352259857563834"><br></div><div id="yMail_cursorElementTracker_0.42352259857563834">Jolayemi Omamuyovwi Rita</div><div id="yMail_cursorElementTracker_0.42352259857563834">University of Benin</div><div id="yMail_cursorElementTracker_0.42352259857563834">Nigeria</div><div id="yMail_cursorElementTracker_0.42352259857563834"><br></div><div id="yMail_cursorElementTracker_0.42352259857563834"><br><div id="ymail_android_signature"><a href="https://overview.mail.yahoo.com/mobile/?.src=Android">Sent from Yahoo Mail on Android</a></div></div>