Self-Assembly of Glycine on Cu (001): the Tales of Polarity and Temperature

TL;DR

This paper investigates how molecular polarity and temperature influence the self-assembly of glycine molecules on Cu(001) surfaces, revealing temperature-dependent structures and mechanisms validated by experiments and simulations.

Contribution

It introduces a unified rule based on polarity compensation to predict glycine self-assembly structures at finite temperatures.

Findings

The room-temperature stable structure differs from the 0 K ground state.

Ab initio molecular dynamics confirms the stability of the p(2X4) structure.

Self-assembly patterns are governed by polarity and temperature effects.

Abstract

Glycine on Cu(001) is used as an example to illustrate the critical role of molecular polarity and finite temperature effect in self-assembly of biomolecules at a metal surface. A unified picture for glycine self-assembly on Cu(001) is derived based on full polarity compensation considerations, implemented as a generic rule. Temperature plays a non-trivial role: the ground-state structure at 0 K is absent at room temperature, where intermolecular hydrogen bonding overweighs competing molecule-substrate interactions. The unique p(2X4) structure from the rule is proved as the most stable one by ab initio molecular dynamics at room temperature, and its STM images and anisotropic free-electron-like dispersion are in excellent agreement with experiments. Moreover, the rich self-assembling patterns including the heterochiral and homochiral phases, and their interrelationships are entirely governed by the same mechanism.