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Register a new userPotassium intercalation in graphite: A van der Waals density-functional study
التداخل البوتاسيوم في الجرافيت: دراسة على أساس الوسيط الكتلي الفونكشنال فان دير والز
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تُشتَغِل التحليل الأولي للمكونات الأساسية في الإدخال البوتاسيوم في الجرافيت. وتحسن الربط في مركب البوتاسيوم والجرافيت بشكل معقول من خلال حسابات الديناميكية المحلية النصفية للديناميكية الكتلية (DFT). ومع ذلك، لاستكشاف طاقة تكوين الإدخال من الأجسام البوتاسيوم النقية والجرافيت، يتطلب استخدام وصف لربط الطبقة الجرافيتية وبالتالي حساباً متناسقاً للتفاعلات التباعدية غير المحلية. ويتم تضمين هذا بشكل سلس مع الديناميكية الكتلية العادية باستخدام تقنية الديناميكية الكتلية الفان دير والس (vdW-DF) [Phys. Rev. Lett. 92، 246401 (2004)]. ووجد أن استخدام vdW-DF يثبط البلور الجرافيتي، مع معاملات البلور في توافق مع التجارب معقول. للجرافيت والجرافيت المحضر بالبوتاسيوم، تشير المعاملات الى مثل فاصل الربط، طاقة ربط الطبقة، طاقة التكوين، والمعامل الحجمي. كما تشير الطاقات الى طاقة الامتصاص والامتصاص الفرعي للبوتاسيوم. ووجد أن وصف vdW-DF، مقارنة مع النهج المحلي النصفي التقليدي، يضعف الاستجابة المرنة بشكل ضعيف.
Potassium intercalation in graphite is investigated by first-principles theory. The bonding in the potassium-graphite compound is reasonably well accounted for by traditional semilocal density functional theory (DFT) calculations. However, to investigate the intercalate formation energy from pure potassium atoms and graphite requires use of a description of the graphite interlayer binding and thus a consistent account of the nonlocal dispersive interactions. This is included seamlessly with ordinary DFT by a van der Waals density functional (vdW-DF) approach [Phys. Rev. Lett. 92, 246401 (2004)]. The use of the vdW-DF is found to stabilize the graphite crystal, with crystal parameters in fair agreement with experiments. For graphite and potassium-intercalated graphite structural parameters such as binding separation, layer binding energy, formation energy, and bulk modulus are reported. Also the adsorption and sub-surface potassium absorption energies are reported. The vdW-DF description, compared with the traditional semilocal approach, is found to weakly soften the elastic response.
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